The Klamath River (Karuk: Ishkêesh, Klamath: Koke) is an American river that flows 263 miles (423 km) southwest through Oregon and northern California, cutting through the Cascade Range to empty into the Pacific Ocean. The river drains an extensive watershed of almost 16,000 square miles (41,000 km2) that stretches from the high desert country of the Great Basin to the temperate rainforest of the Pacific coast. It is known for its basin's peculiar geography—most of its upper basin is developed, but the lower remains wild—and has been called "a river upside down" by the National Geographic Society. As one of the most important rivers for fish migration on the west coast of North America south of the Columbia River, the Klamath River basin has been inhabited by humans for at least 7,000 years. At one time, the river supported abundant wildlife. Vast freshwater marshes in the upper basin provided habitat for thousands of migratory birds. The first Europeans to visit the region were fur trappers for the Hudson's Bay Company who came in the 1820s and established the Siskiyou Trail along the Klamath and Trinity Rivers into the Sacramento Valley. The latter days of the California Gold Rush saw increasing numbers of miners working streams in the Klamath River region in search of gold. Steamboats operated briefly on the large lakes in the upper watershed before the establishment of agriculture in the 19th and 20th centuries. The growing industry in the upper basin led to the construction of many dams on the river, which have since caused water quality issues for the lower river. Environmentalists have raised petitions against the construction of more dams, and in support of removing the existing ones. Because the Klamath includes many of the longest free-flowing stretches of river in California as well as some of its better whitewater runs, it has become a popular recreational river. Its watershed includes large swathes of the Klamath National Forest and Six Rivers National Forest. For now, the lower Klamath remains undeveloped, although massive diversions were once proposed to reroute the river into the Central Valley in order to supplement the region's water supply.