The San Joaquin River is one of the largest rivers in the state of California. It originates high on the western slope of the Sierra Nevada, in the Ansel Adams Wilderness near Mammoth Mountain. The San Joaquin river drains most of the area from the southern border of Yosemite, south to Kings Canyon National Park, making it the second largest river drainage in the state. It emerges from the foothills at what was once the town of Millerton, now the location of Friant Dam and Reservoir.

The river flows west to the trough of the Central Valley, where it is joined by the Sierra's other great rivers and then flows north to the Sacramento-San Joaquin Delta and then San Francisco Bay. A ship channel makes the river navigable for ocean freighters as far inland as Stockton.

Since the mid-19th century, the waters of the San Joaquin have been extensively manipulated and diverted for human use. As a result of these activities, by 1928, the California Department of Fish and Game had issued a bulletin reporting that there were "very few" salmon remaining in the San Joaquin River above the Merced River and the "historical" salmon fishery that once existed had been "severely depleted." Although some sources claim that the river may have once supported large runs of both fall-run and spring-run Chinook salmon -- up to 300,000 returning adults annually -- these claims appear to be greatly exaggerated, given the river's hydrology, San Joaquin Valley temperatures, and the impacts of these factors on available fish habitat. An official with the California Department of Fish and Game stated in 1930s that the spawning gravels in the river were only sufficient to support, at most, about 15,000 returning fish. During that same time (late 1930s - early 1940s), the salmon counts taken by the California Department of Fish and Game at the Mendota Dam fish ladder showed about 3,000-7,000 salmon returning each year to spawn.

Steelhead trout may have also been present in the river in the 19th century, although there is no known evidence to confirm this hypothesis.

See also

• List of California rivers