USUMACINTA RIVER

Spanish Ro Usamacinta, river in southeastern Mexico and northwestern Guatemala, formed by the junction of the Pasin River, which arises in the Sierra de Santa Cruz (in Guatemala) and the Salinas River, also known as the Chixoy, or the Negro, which descends from the Sierra Madre de Guatemala. The Usumacinta River flows northwestward, receiving the Lacantum River and forming the border between Mexico and Guatemala. Below the ruins of Piedras Negras, located in Guatemala, the river begins its meandering course through the swampy lowlands of the southern shores of the Bay of Campeche. It forms the ChiapasTabasco border and continues generally northwestward. The main arm joins the Grijalva River and empties into the Bay of Campeche below Frontera; the central arm, called San Pedro y San Pablo, flows into the bay at the town of San Pedro; and the eastern arm, the Palizada, empties into the Trminos Lagoon in Campeche state. The total length of the main channel, including the Chixoy, is approximately 600 miles (1,000 km). Navigable for 300 miles (480 km) inland, the Usumacinta has had great economic significance as a means of communication for the towns on its banks and for exporting logs, chicle, and other lowland products.