river in central Alaska, U.S. A major tributary of the Yukon River, it rises from several headstreams on the southern slopes of the Endicott Mountains in the central Brooks Range and flows southwestward through Gates of the Arctic National Park and Preserve and Koyukuk National Wildlife Refuge for about 550 miles (885 km) to join the Yukon near the village of Koyukuk. Named for the Koyukon, an Athabascan Indian people, the river was visited in 1842–44 by the Russian explorer Lavrenty Zagoskin. Placer deposits in the upper Koyukuk basin, discovered in 1898 during the gold rush, have been worked near the settlements of Wiseman and Allakaket, though they are not of commercial importance. The Trans-Alaska Pipeline crosses the northeastern section of the Koyukuk drainage basin. The river, which drains an area of some 35,000 square miles (91,000 square km), is underlain by continuous permafrost. Flooding of the river in 1994 devastated several villages along its banks, including Allakaket and Alatna.