YU-MEN

Pinyin Yumen, city in western Kansu sheng (province), China. It is situated on the ancient Silk Road from China into Central Asia. It was first brought under Chinese control in the last years of the 2nd century BC when it was given the name Y-men (Jade Gate). Known as Hui-chi county in the 5th century AD, when the area was recovered by the Northern Wei dynasty, it was renamed Y-men in 581. Under the T'ang dynasty (618907), Y-men county's seat was at Ch'ih-chin-shan, east of the modern city. After about 770 the area fell to the Tibetans, who retained control for some 70 years; and after the end of the T'ang dynasty in 907, Y-men became a part of the Hsi-Hsia (Tangut) state. During the Ming period (13681644) it again became a Tibetan territory, and the county was only reestablished in the early Ch'ing (16441911) period. Until the end of the T'ang dynasty the overland route to western Asia flourished, and Y-men consequently also prospered. When sea transport subsequently replaced the old route, however, Y-men became a backwater, although the establishment of Ch'ing hegemony in Central Asia to some extent revived the overland route. Two important developments in the late 1930s and 1940s led to the city's spectacular revival. The first was the construction of a modern highway, paved as far west as Y-men, along the old caravan route to Urumchi (Wu-lu-mu-ch'i), and continuing westward to what is now Kazakstan. This became a vital supply line during World War II, and since 1949 the highway has been improved, and its line has been followed by a railway joining Lan-chou in Kansu to Urumchi, now in the Uighur Autonomous Region of Sinkiang. The second was the discovery of oil in the Chiu-ch'an basin, to the north of the Nan Shan Mountains. The first oil was drilled at Lao-chn-miao near Y-men in 1939. Appreciable production was achieved by 1941, but it was only after 1949 that large-scale development began. Prospecting after 1950 revealed vastly larger reserves than had been suspected. Y-men has its own refinery, but the fields are also linked to the major refinery at Lan-chou by a pipeline, and some of the crude oil is shipped by rail for refining. The Y-men Oil Administration also has general control over the Karamay (K'o-la-ma-i) field in western Sinkiang. To staff new oil fields, a university established in 1970 gives courses in mechanics and undergound operations. Pop. (1990 est.) 109,234.