The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about long. Its length to its most distant headwater tributary is just over . The main stem Feather River begins in Lake Oroville, where its four long tributary forks join—the South Fork, Middle Fork, North Fork, and West Branch Feather Rivers. These and other tributaries drain part of the northern Sierra Nevada, and the extreme southern Cascades, as well as a small portion of the Sacramento Valley. The total drainage basin is about , with approximately above Lake Oroville. The Feather River and its forks were a center of gold mining during the 19th century. Since the 1960s, the river has provided water to central and southern California, as the main source of water for the California State Water Project. Its water is also used for hydroelectricity generation. The average annual flow of the Feather River is more than 7 million acre feet (3.3 km3). The Feather is unique in that two of its tributaries, the East Branch and Middle Fork, originate east of the Sierra Nevada in the Diamond Mountains and breach the crest of the Sierra as they flow west. Course The river rises in four main forks in the Sierra Nevada which unite as arms of the Lake Oroville reservoir in the foothills northeast of Oroville in eastern Butte County. In terms of drainage areas the largest is the North Fork, which drains about 60% of the entire upper Feather River watershed. The Middle Fork is the second largest, draining about 32% of the upper basin. The South Fork and the West Branch are much smaller, each drains less than 5% of the upper basin. The main stem Feather River begins at Oroville Dam, the outlet of Lake Oroville. From there the river flows generally south across the Sacramento Valley, east of the Sutter Buttes, past Oroville and Yuba City–Marysville. The Feather receives the Yuba River from the east at Yuba City and the Bear River from the east south of Yuba City. It empties into the Sacramento River from the north, about northwest of Sacramento. North Fork The North Fork Feather River begins in Feather River Meadows at the junction of Rice Creek and South Arm Rice Creek, . The names and confluence locations of the streams in this area were changed by