Sacramento, longest river of Calif., c.380 mi (610 km) long, rising near Mt. Shasta, N Calif., and flowing generally SW to Suisun Bay, an arm of San Francisco Bay, where it forms a large delta with the San Joaquin River. Its chief tributaries are the Pit, Feather, McCloud, and American rivers. At high water the river is navigable by small steamers c.260 mi (420 km) to Red Bluff. The valley saw the great gold strike of 1848, and many of the cities on or near the river and its tributaries sprang up in the gold rush; Sacramento is the largest. This northern part of the Central Valley of California, known as the Sacramento Valley, has been developed as a fertile agricultural region. The Central Valley project was developed to use the waters of the Sacramento with greater efficiency, particularly in the fertile but dry southern part of the Central Valley, known as the San Joaquin Valley. Shasta Dam and Keswick Dam on the Sacramento are major units of the project; they also generate electricity.