NORTH AMERICA

third in size among the world's continents, lying for the most part between the Arctic Circle and the Tropic of Cancer, extending for more than 5,000 miles (8,000 km) to within 500 miles of both the North Pole and the Equator, and covering an area of 9,355,000 square miles (24,230,000 square km). For current history and for statistics on society and economy, see Britannica Book Of The Year. Except where the relatively narrow Isthmus of Panama extends southeastward to connect with Colombia in South America, the continent, shaped like an inverted triangle, is completely surrounded by water. The Pacific Ocean extends the length of its western coast, the narrow Bering Strait separates it from Russia and Asia to the northwest, the Arctic Ocean and several of the continent's major islands lie to the north, the Atlantic Ocean lies to the east, and the Caribbean Sea and the Gulf of Mexico are situated in the southeast. The population in 1990 for the entire continent was estimated to be 424,523,000, or about one-twelfth of the world's population. third in size among the world's continents, lying for the most part between the Arctic Circle and the Tropic of Cancer. It extends for more than 5,000 miles (8,000 kilometres) to within 500 miles of both the North Pole and the Equator and has an east-west extent of 5,000 miles. It covers an area of 9,355,000 square miles (24,230,000 square kilometres). North America occupies the northern portion of the landmass generally referred to as the New World, the Western Hemisphere, or simply the Americas. Mainland North America is shaped roughly like a triangle, with its base in the north and apex in the south; associated with the continent is Greenland, the largest island in the world, and such offshore groups as the Arctic Archipelago, the Bahamas, the Greater and Lesser Antilles, the Queen Charlotte Islands, and the Aleutian Islands. North America is bounded on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west by the North Pacific Ocean. To the northeast, Greenland is separated from Iceland by the Denmark Strait, and to the northwest, Alaska is separated from the Asian mainland by the much narrower Bering Strait; North America's only land connection is to South America at the narrow Isthmus of Panama. Mount McKinley in Alaska, at 20,320 feet (6,194 metres) above sea level, is the continent's highest point; and Death Valley in California, at 282 feet (86 metres) below sea level, is its lowest. North America's coastline of some 37,000 milesthe second longest of the continents after Asiais notable for the great number of indentations, particularly in the northern half. The name America is derived from that of the Italian merchant and navigator Amerigo Vespucci, one of the earliest European explorers to the New World. Although at first the term America was applied only to the southern half, the designation soon was applied to the entire landmass; those portions that widened out north of the Isthmus of Panama became known as North America, and those that broadened to the south became known as South America. According to some authorities, North America begins not at the Isthmus of Panama but at the narrows of Tehuantepec, with the intervening region called Central America. Under such a definition, part of Mexico must be included in Central America, although that country lies mainly in North America proper. To overcome this anomaly, the whole of Mexico, together with Central and South American countries, also may be grouped under the name Latin America, with the United States and Canada referred to as Anglo-America. This cultural division is a very real one; yet Mexico and Central America (including the Caribbean) are bound to the rest of North America by strong ties of physical geography. Greenland also is culturally divided from, but physically close to, North America. North America was the first continent to achieve its current approximate size and shape, and it contains some of the oldest rocks on the Earth. Its geologic structure is built around a stable platform of Precambrian rock called the Canadian (Laurentian) Shield. To the southeast of this rose the ancient Appalachian Mountains; and to the west rose the younger and considerably taller Cordilleras, which occupy nearly a third of the continent's land area. In between these two mountain belts are the generally flat regions of the Great Plains in the west and the Central Lowlands in the east. The continent is richly endowed with natural resources, including great mineral wealth, vast forests, immense quantities of fresh water, and some of the world's most fertile soils. These have allowed North America to become one of the most economically developed regions in the world, and its inhabitants enjoy a high standard of living. North America has the highest average income per person of any continent and a food intake per person considerably greater than the average for Asia. Although it is home to less than 10 percent of the world's population, its per capita consumption of energy is almost six times as great as the average for all the other continents. North America's first inhabitants are believed to have been ancient Asiatic peoples who migrated from Siberia to North America sometime during the last (Wisconsin) glacial advance. The descendants of these peoples, the various Indian and Eskimo peoples, largely have been supplanted by peoples from the Old World. People of European ancestry constitute the largest group, followed by those of African and of Asian ancestry; in addition there is a large group of Latin Americans, who are of mixed European and Indian ancestry. James Wreford Watson The Editors of the Encyclopdia Britannica This article treats the physical and human geography of North America. For discussion of individual countries of the continent, see the articles Canada, Mexico, and United States of America. See also coverage of North American regions under the titles Central America and West Indies. For discussion of major cities of the continent, see specific articles by namee.g., Mexico City, New York City, and Toronto. For discussion of the indigenous peoples of the continent, see the articles Native American and Pre-Columbian Civilizations. The principal treatment of North American historical and cultural development is contained in the articles mentioned above and in the article Latin America, history of. For further discussion of arts and literature, see the articles American literature; Native American arts; Canadian literature; and Latin-American literature. Additional reading General works Fred W. Headon, Continent of Contrast: A Study of North America (1985), is a traditional geography text, treating the continent as divided into eight main regions and discussing the physical and human environment for each region. J.H. Paterson, North America: A Geography of the United States and Canada, 8th ed. (1989), is similar, with more of the focus on human aspects. American Geographical Society of New York, Readings in the Geography of North America: A Selection of Articles from the Geographical Review (1952), presents classic scholarly papers on a wide range of topics. J. Wreford Watson, North America, rev. ed. (1967); and Tom L. McKnight, Regional Geography of the United States and Canada (1992), are literate and comprehensive works. Joel Garreau, The Nine Nations of North America (1981), a highly readable journalistic work, explores the feasibility of rearranging the continent into regional political units.National Geographic Society (U.S.), Atlas of North America (1985), contains a variety of highly detailed maps and satellite-imagery photographs. Atlases of large portions of North America include Geological Survey (U.S.), The National Atlas of the United States (1970), still useful despite some gaps in coverage and the aging of much data; Canada, Energy, Mines, and Resources Canada, The National Atlas of Canada, 5th ed. (1985 ); James B. Pick, Edgar W. Butler, and Elizabeth L. Lanzer, Atlas of Mexico (1989); and Stanley A. Arbingast et al., Atlas of Central America (1979). Randall John Schaetzl Wilbur Zelinsky Geologic history The Geological Society of America and the Geological Survey of Canada have undertaken the publication of a monumental, multivolume series, The Geology of North America (1986 ), covering also the surrounding oceans. The series presents an up-to-date synthesis of research in the field, and, when completed, will provide the most comprehensive coverage of the subject. Albert W. Bally and Allison R. Palmer (eds.), The Geology of North America (1989), is an overview volume in the series. Among the other published volumes are Peter R. Vogt and Brian E. Tucholke (eds.), The Western North Atlantic Region (1986); W.F. Ruddiman and H.E. Wright, Jr. (eds.), North America and Adjacent Oceans During the Last Deglaciation (1987); William Back, Joseph S. Rosenshein, and Paul R. Seaber (eds.), Hydrogeology (1988); Robert E. Sheridan and John A. Grow (eds.), The Atlantic Continental Margin: U.S. (1988); L.L. Sloss (ed.), Sedimentary Cover, North American Craton, U.S. (1988); R.J. Fulton (ed.), Quaternary Geology of Canada and Greenland (1989); Robert D. Hatcher, Jr., William A. Thomas, and George W. Viele (eds.), The Appalachian-Ouachita Orogen in the United States (1989); E.L. Winterer, Donald M. Hussong, and Robert W. Decker (eds.), The Eastern Pacific Ocean and Hawaii (1989); Gabriel Dengo and J.E. Case (eds.), The Caribbean Region (1990); Arthur Grantz, L. Johnson, and J.F. Sweeney (eds.), The Arctic Ocean Region (1990); M.J. Keen and G.O. Williams (eds.), Geology of the Continental Margin of Eastern Canada (1990); M.G. Wolman and H.C. Riggs (eds.), Surface Water Hydrology (1990); H.J. Gluskoter, D.D. Rice, and R.B. Taylor (eds.), Economic GeologyU.S. (1991); Roger B. Morrison (ed.), Quaternary Nonglacial Geology: Conterminous U.S. (1991); Guillermo P. Salas (ed.), Economic Geology, Mexico (1991; originally published in Spanish, 1988); Amos Salvador (ed.), The Gulf of Mexico Basin (1991); H.P. Trettin (ed.), Geology of the Innuitian Orogen and Arctic Platform of Canada and Greenland (1991); B.C. Burchfiel, P.W. Lipman, and M.L. Zoback (eds.), The Cordilleran Orogen, Conterminous U.S. (1992); H. Gabrielse and C.J. Yorath (eds.), Geology of the Cordilleran Orogen in Canada (1992); John C. Reed, Jr., et al. (eds.), Precambrian: Conterminous U.S. (1993); D.F. Scott and J.D. Aitken (eds.), Sedimentary Cover of the Craton in Canada (1993); George Plafker and Henry C. Berg (eds.), The Geology of Alaska (1994); and Harold Williams (ed.), Geology of the Appalachian-Caledonian Orogen in Canada and Greenland (1995).Useful works other than those of this series include G. Choubert and A. Faure-Muret (eds.), Geological World Atlas (1976 ), with a section illustrating North America; Philip B. King, The Tectonics of North America (1969), written to accompany a map, and The Evolution of North America, rev. ed. (1977), both masterpieces whose scholarship predates the concept of plate tectonics; and Arthur Escher and W. Stuart Watt (eds.), Geology of Greenland (1976), a comprehensive and well-illustrated study. Paul F. Hoffman The land Charles B. Hunt, Natural Regions of the United States and Canada (1974), offers comprehensive, if a bit dated, reference-quality coverage of soils, geology, climate, vegetation, and resources. Wallace W. Atwood, The Physiographic Provinces of North America (1940), presents a classic geographic approach to the geologic and geomorphic regions and to the landforms and their formation. Studies with a more specific focus include William Wyckoff and Larry M. Dilsaver (eds.), The Mountainous West: Explorations in Historical Geography (1995); Ralph C. Heath, Ground-Water Regions of the United States (1984), an excellent brief summary; Howard B. Sprague (ed.), Grasslands of the United States: Their Economic and Ecologic Importance (1974), a good review provided in a collection of symposium papers; United States, Soil Conservation Service, Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys (1975, reprinted 1988), a definitive guide, according to the United States Department of Agriculture; and Canadian Agricultural Services Coordinating Committee, Expert Committee on Soil Survey, The Canadian System of Soil Classification, 2nd ed. (1987), a similar Canadian guide. Works on the climate include W.G. Kendrew and B.W. Currie, The Climate of Central Canada: Manitoba, Saskatchewan, Alberta, and the Districts of Mackenzie and Keewatin (1955); W.G. Kendrew and D. Kerr, The Climate of British Columbia and the Yukon Territory (1955); Stephen S. Visher, Climatic Atlas of the United States (1954, reprinted 1966); and United States, Environmental Data Service, Climatic Atlas of the United States (1968, reprinted 1983).The flora and fauna are described in Richard J. Preston, Jr., North American Trees: Exclusive of Mexico and Tropical Florida, 4th ed. (1989), a good reference text on habitats, taxonomy, and distribution of major forest trees and shrubs; H.A. Fowells (compiler and ed.), Silvics of Forest Trees of the United States (1965, reprinted 1975), a classic work on the ecology, distribution, and study of the environmental requirements and processes of tree growth of most, if not all, of the tree species found in the region; John L. Vankat, The Natural Vegetation of North America (1979), a survey of the geography and ecology of major plant communities; E. Raymond Hall, The Mammals of North America, 2nd ed., 2 vol. (1981), a comprehensive study; Ralph S. Palmer (ed.), Handbook of North American Birds (196288), the most thorough treatment of birdlife, although not all genera are included; and Howard P. Brokaw (ed.), Wildlife and America: Contributions to an Understanding of American Wildlife and Its Conservation (1978). Gary A. Klee, Conservation of Natural Resources (1991), focuses mostly on the United States, but the concepts discussed are applicable to the whole of the continent. Randall John Schaetzl The people Robert D. Mitchell and Paul A. Groves (eds.), North America: The Historical Geography of a Changing Continent (1987), collects 18 chronologically arranged essays treating the development of the United States and Canada over time and space from the days of early European exploration to the late 20th century. D.W. Meinig, The Shaping of America: A Geographical Perspective on 500 Years of History (1986 ), explores geographic influences on continental history in eloquent prose and with imaginative graphics. The demographic, economic, and political history of the continent is well illustrated in Charles O. Paullin and John K. Wright (eds.), Atlas of the Historical Geography of the United States (1932, reprinted 1975), a monument of historical and geographic scholarship; National Geographic Society (U.S.), Historical Atlas of the United States (1988), a visually appealing volume with informative bibliographic references; Edwin Scott Gaustad, Historical Atlas of Religion in America, rev. ed. (1976), an expert analysis of the principal U.S. denominations and some general aspects of religion in the United States; and James Paul Allen and Eugene James Turner, We the People: An Atlas of America's Ethnic Diversity (1988), a superlative work which offers scores of full-colour county- and state-level maps, along with text, covering a multitude of ethnic groups. Other works of interest are Stephan Thernstrom (ed.), Harvard Encyclopedia of American Ethnic Groups (1980), which presents detailed reference essays by authoritative scholars; William C. Sturtevant et al. (eds.), Handbook of North American Indians (1978 ), encyclopaedic coverage using both the topical and tribal approach; and Joseph J. Spengler, Population and America's Future (1975), a thoughtful evaluation of U.S. demographic patterns and trends and their implications for the national welfare.Broad looks at the culture of the continent include Wilbur Zelinsky, The Cultural Geography of the United States, rev. ed. (1992), exploring the historical and spatial development of the American cultural system and its special characteristics, while also offering bibliographic guidance to the literature; Michael A. Goldberg and John Mercer, The Myth of the North American City (1986), a superb comparative study that describes and attempts to explain the obvious sharp differences in the ways Canadian and U.S. cities look and function; Joel Garreau, Edge City: Life on the New Frontier (1991), a penetrating look at the changing U.S. metropolis, with the unprecedented mushrooming of virtually autonomous cities along the rims of metropolitan areas; and John Herbers, The New Heartland: America's Flight Beyond the Suburbs and How It Is Changing Our Future (1986), a thoughtful treatment of the exurbanization of the U.S. population and its implications. John R. Stilgoe, Common Landscape of America, 15801845 (1982), is an ambitious attempt to describe and explain the full range of the built-up landscape in its historical and regional dimensions; while Michael P. Conzen, The Making of the American Landscape (1990), collects 18 original essays on the creation of North American built-up landscapes, past and present. Specific features of culture are explored in Craig M. Carver, American Regional Dialects: A Word Geography (1987), which interprets the findings of a massive lexicographic project and discusses language development over the vast territory; Charles Reagan Wilson and William Ferris (eds.), Encyclopedia of Southern Culture (1989), a monumental compendium of engrossing information; and Alan Gowans, Images of American Living: Four Centuries of Architecture and Furniture as Cultural Expression (1964, reissued 1976), a profound treatment of the meaning of these aspects of material culture. The economy Brian J.L. Berry, Edgar C. Conkling, and D. Michael Ray, The Geography of Economic Systems (1976), is a general theoretical text, with detailed case studies including a survey of North America's industrial heartland. Another broad study is Ann Markusen, Regions: The Economics and Politics of Territory (1987), an enterprising economist's effort to come to grips with the stubborn reality of regional differences and their economic and political implications. The relationship between the main sectors of economy and their locations is explored in Howard F. Gregor, Geography of Agriculture (1970), an informative introduction, with most examples focusing on North America; E. Willard Miller, Manufacturing: A Study of Industrial Location (1977), a standard text with special emphasis on the U.S. scene; Ann Markusen, Peter Hall, and Amy Glasmeier, High Tech America: The What, How, Where, and Why of the Sunrise Industries (1986), an excellent economic geography; Susan Hanson (ed.), The Geography of Urban Transportation (1986), a collection of original essays focusing on the U.S. situation; and James E. Vance, Jr., Capturing the Horizon: The Historical Geography of Transportation Since the Transportation Revolution of the Sixteenth Century (1986), a comprehensive study of the topic, with ample attention to North America, and The Merchant's World: The Geography of Wholesaling (1970), a provocative theoretical and historical treatment with special reference to the United States.Discussions of resources and their exploitation are found in Leonard L. Fischman (ed.), World Mineral Trends and U.S. Supply Problems (1980), a consideration of long-term potential supply and price problems for seven major nonfuel minerals; Minerals Yearbook, offering detailed annual surveys of the mineral industries of the United States and the world; Michael Williams, Americans and Their Forests: A Historical Geography (1989), a definitive monograph on all aspects of U.S. forests and their exploitation, past and present; Gordon G. Whitney, From Coastal Wilderness to Fruited Plain: A History of Environmental Change in Temperate North America, 1500 to the Present (1994), also focusing on the forests; Rexford Daubenmire, Plant Geography: With Special Reference to North America (1978), a standard text on the subject; John W. Barrett (ed.), Regional Silviculture of the United States, 2nd ed. (1980), an assessment of the biological, physical, and economic qualities of the forested regions of the country; James J. Geraghty et al., Water Atlas of the United States, new ed. (1973), a compendium of atmospheric, hydrologic, and water-use data; and Water Resources Council (U.S.), The Nation's Water Resources, 19752000: Second National Water Assessment, 4 vol. in 29 (1978), a comprehensive appraisal.Earl Cook, Man, Energy, Society (1976), presents a broad review of the role of energy in modern society, with an emphasis on the fossil fuels and energy policy questions that face the United States. David J. Cuff and William J. Young, The United States Energy Atlas, 2nd ed. (1986), offers comprehensive coverage of energy resources, production, transport, consumption, and other relevant topics using maps, graphs, and text. Philip R. Pryde, Nonconventional Energy Resources (1983), is a broad survey of solar, wind, geothermal, hydroelectric, biomass, nuclear, electrochemical, and oceanic energy resources. Wilbur Zelinsky The economy Few episodes in human history have been more remarkable than the economic transformation of North America since about 1700. During the pre-Columbian period, the territories that became the United States and Canada (sometimes called Anglo-America) were areas thinly settled by an aboriginal population that just had begun to practice agriculture on a local scale. In contrast, comparatively old and complex agrarian and urban civilizations had arisen in portions of Mexico and Central America, where relatively elaborate economies and dense populations had developed. The revolutionary changes occurring after European contact and occupation were the result of an extraordinary combination of circumstances, at least in the United States and Canada. The large numbers of energetic immigrants from a rapidly modernizing western Europe, who brought with them the newest technological advances, encountered a habitat that afforded them ample opportunity to create considerable wealth. Many of the vast regions they encountered were well watered, covered by rich, exploitable forests and productive soils; underlain by considerable mineral resources; and blessed with a climate tolerable to Europeans. Moreover, the configuration of ocean shorelines, rivers, lakes, and landforms rendered feasible the construction of a dense and efficient transportation system for both domestic and foreign commerce. In addition, throughout nearly all of this economic transformation, the huge expanse of the continent north of Mexico has been controlled by two remarkably compatible nationsthe United States and Canadawhich, in their political orientations, have actively promoted aggressive economic development. The outcome of all of these circumstances has been a level of physical well-being for their citizens that ranks among the highest in the world. Finally, during much of the 20th century the United States has been the world's dominant power in terms of financial resources and economic influenceas well as in agricultural, mineral, and industrial outputand in general it has been the locus of an inordinate share of worldwide production and consumption. Since the time of the Spanish conquest, the economic development in Mexico, Central America, and the Caribbean regionwhich constitute the northern portion of what often is called Latin Americahas been much less pronounced. The failure to attract large numbers of immigrants (aside from African slaves and East Asian labourers in the West Indies), the fragmentation of Central America and the Caribbean into small colonies or sovereign nations, and the perennial political instability throughout the region have all inhibited development. The quantity or quality of natural resources has been less crucial than social and political factors in relegating these lands to peripheral or so-called underdeveloped status within the world economy. (New England, for example, prospered despite distinctly mediocre physical resources.) Whatever economic well-being these Latin American and West Indian countries now enjoy depends to a large extent on the export of minerals and the products of plantations, forests, and the sea and on the infusion of foreign capital and expertise. This has given rise to an economic system in which only a small number of individuals in certain advantaged areas of the region have benefited from the wealth generated by economic development, while the great majority of the region's population has remained impoverished and little affected. This so-called core-periphery model of development also is evidentthough to a lesser extentin the United States and Canada. Large disparities in social and economic attainment exist between such generally affluent areas as the northeastern Atlantic Seaboard of the United States, the California coast, and the more urbanized areas of Ontario and Quebec and such economically depressed regions as the southern Appalachian Mountains, the lower Mississippi River valley, and Newfoundland. On a smaller scale, notable differentials can be discerned among neighbourhoods in individual cities and among communities within urban areas. Resources North America has rich and varied resources. Although it contains less than 10 percent of the world's population, it has an extraordinarily high proportion of the world's resource wealth. It produces a substantial percentage of the world's oil, iron ore, steel, copper, lead, and zinc. With a large percentage of the world's coal and oil output and electrical power production, it possesses the critical elements of modern industry. The land Although the geologic processes that shaped the North American continent have been so important that the 19th-century American historian Frederick Jackson Turner once contended that the life of America flowed down the arteries of its geology, the continent nevertheless has been altered considerably by climate and drainage and, to some extent, by soils and vegetation. The resultant physiographic regions dominate the contemporary geography of the continent. Relief The central shield The central shield consists of a low plateau (averaging 1,400 feet in elevation) that is tilted at its edges and sinks down to Hudson Bay at its centre. It has a rough surface of old worn mountains and domes that rise above flat, geologically ancient basins. The shield represents an area that has undergone extensive erosion and sculpting by ice and weathering processes. The southern edge has the mountainous Algomans and Laurentians (more than 2,000 feet) and rises to above 5,000 feet in the great dome of the Adirondacks. The eastern edge is somewhat higher, rising to nearly 6,000 feet in the Torngats and more than 7,000 feet in Baffin Island; in Greenland, too, it tilts up to more than 6,000 feet. The western rim is much lower, reaching only about 600 feet in parts. The Snare and Nonacho ranges west of Hudson Bay lift the edge of the plateau to nearly 2,000 feet. Faulting broke the northern rim into a series of prongs, extending into southeastern Ellesmere Island and across Victoria Island, with sea-drowned channels and low sedimentary basins in between forming the Canadian Arctic Archipelago. The entire shield was under successive ice sheets during the Pleistocene Epoch (1,600,000 to 10,000 years ago), and its high eastern rim still contains relics of these glacial advances and retreats. Ice-cut valleys in the higher areas, ice-plucked basins everywhere, and ice-deposited ridges known as eskers and drumlins point to a major centre of ice accumulation and dispersion over central Labrador, still noted for its heavy snow cover. Greenland also was a main centre of glacial advance and retreat, while Keewatin in western Canada was an important secondary focus. After most of the ice had melted and its tremendous weight had been lifted from the crust, portions of the shield began to rise, leaving traces of former beaches along the coasts of Greenland, Baffin Island, Labrador, and the Gulf of St. Lawrence; these provided narrow but vital benches for human settlement. Ice-cut rock basins have left countless lakes, and parts of the surface of the central shield are almost more water than land. The people In global terms, North America long remained a relatively empty and economically undeveloped land until about AD 1500. After that the continent began to receive great numbers of people from the Old Worldprimarily Europe and Africaand it underwent a profound transformation. The discussion that follows primarily covers the nonindigenous peoples of mainland North America. The ethnohistory of the North American Indians is treated in more detail in the article Native American, and that of the Mesoamerican peoples is discussed in Pre-Columbian Civilizations; for treatment of the peoples in the Caribbean region, see West Indies. The North American Indian heritage The date of the arrival in North America of the initial wave of peoples from whom the American Indians (or Native Americans) emerged is still a matter of considerable uncertainty. It is relatively certain that they were Asiatic peoples who originated in northeastern Siberia and crossed the Bering Strait (perhaps when it was a land bridge) into Alaska and then gradually dispersed throughout the Americas. The glaciations of the Pleistocene Epoch (1,600,000 to 10,000 years ago) coincided with the evolution of modern humans, and ice sheets blocked ingress into North America for extended periods of time. It was only during the interglacial periods that people ventured into this unpopulated land. Some scholars claim an arrival before the last (Wisconsin) glacial advance, about 60,000 years ago. The latest possible date now seems to be 20,000 years ago, with some pioneers filtering in during a recession in the Wisconsin glaciation. These prehistoric invaders were Stone Age hunters who led a nomadic life, a pattern that many retained until the coming of Europeans. As they worked their way southward from a narrow, ice-free corridor in what is now the state of Alaska into the broad expanse of the continentbetween what are now Florida and Californiathe various communities tended to fan out and to hunt and forage in comparative isolation. Until they converged in the narrows of southern Mexico and the confined spaces of Central America, there was little of the fierce competition or the close interaction among groups that might have stimulated cultural inventiveness. Although great architectural and scientific advances did occur in Mesoamerica, there was markedly less in the way of metallurgy, transportation networks, and complex commerce than among the contemporary civilizations of Asia, Europe, and sections of Africa. Cities appeared first among the Olmec in the strategic narrows between Mexico and Central America and among the Maya in portions of Guatemala, the Yucatn Peninsula, and Honduras. Subsequently, the Toltec and Aztec created some remarkable cities in the high Mexican Plateau and developed a society whose crafts and general sophistication rivaled those of Europe. These dense populations were based on a productive agriculture that relied heavily on corn (maize), beans, and squash, along with a great variety of other vegetables and fruits, fibres, dyes, and stimulants but almost no livestock. The size of the pre-Columbian aboriginal population of North America remains uncertain, since the widely divergent estimates have been based on inadequate data. Luis de Velasco, a 16th-century viceroy of New Spain (Mexico), put the total for the West Indies, Mexico, and Central America at about 5,000,000; some modern scholars, however, have suggested a figure two to five times larger for the year 1492. The pre-Columbian population of what is now the United States and Canada, with its more widely scattered societies, has been variously estimated at somewhere between 600,000 and 2,000,000. By that time, the Indians there had not yet adopted intensive agriculture or an urban way of life, although the cultivation of corn, beans, and squash supplemented hunting and fishing throughout the Mississippi and Ohio river valleys and in the Great LakesSt. Lawrence river region, as well as along the Gulf of Mexico and Atlantic Coastal Plain. In those areas, semisedentary peoples had established villages, and, among the Iroquois and the Cherokee, powerful federations of tribes had been formed. Elsewhere, however, on the Great Plains, the Canadian Shield, the northern Appalachians, the Cordilleras, the Great Basin, and the Pacific Coast, hunting, fishing, and gathering constituted the basic economic activity; and, in most instances, extensive territories were needed to feed and support small groups. The history of the entire aboriginal population of North America after the Spanish conquest has been one of unmitigated tragedy. The combination of susceptibility to Old World diseases, loss of land, and the disruption of cultural and economic patterns caused a drastic reduction in numbersindeed, the extinction of many communities. It is only since about 1900 that the numbers of some Indian peoples have begun to rebound.