Salmon Creek starts at an elevation of 570 feet (174 m) and flows generally southwest for 19 miles (31 km) draining a watershed of 22,487 acres (9,100 ha) between the Northern Coast Ranges and the Pacific Ocean at Salmon Creek Beach in Sonoma Coast State Park, about 20 miles (32 km) southwest of Santa Rosa and 2 miles (3.2 km) northwest of Bodega Bay, California. Salmon Creek is named after the historical runs of steelhead trout and coho salmon. The stream has no impoundment dams, although there are 43 active water diversions for domestic and agricultural water supply. The watershed is characterized by scattered rural development amidst pasture, vineyards, and mixed hardwood and redwood forests. The upper watershed is underlain by rocks of the Wilson Grove Formation that developed during the late Miocene to late Pliocene and consists of unconsolidated fine-grained sand and minor amounts of gravel and tuff deposited under beach and shallow-marine conditions. The formation overlies the Franciscan Complex that is exposed along the coast and consists of greywacke sandstones, shales and conglomerates that developed between the Eocene to late Cretaceous and which have experienced low-grade metamorphism.

The Coast Miwok village of Pulya-lakum was historically located near the mouth of Salmon Creek. In 1812, the Russian-American Company established Fort Ross about 12 miles (19 km) north of present-day Salmon Creek as an agricultural base for the northern settlements in Alaska while also continuing trade with the Franciscan missions of Spanish Alta California. Following the War of Independence from Spain in 1821, the Mexican government found evidence of Russian encroachment with at least three farms established inland from Fort Ross, including one on Salmon Creek. To counter the Russian expansion, land grants were given to prominent citizens and military veterans. In 1844, a Mexican land grant of 35,487 acres (14,361 ha) named Rancho Bodega was given by Governor Manuel Micheltorena to Captain Stephen Smith. The grant extended along the Pacific coast from the Russian River in the north to Estero Americano on Bodega Bay in the south. Smith built the first steam-powered sawmill in California in the redwoods on Salmon Creek. When Captain Smith died in 1855, his widow, Manuela Torres, married Tyler Curtis, and when Mexico ceded Alta California to the United States in 1848, he received the land patent for Rancho Bodega. Curtis tried to evict squatters and settlers who were farming parcels on the rancho and hired an enforcement militia of about forty men in what became known as the Bodega War. However, about 200 settlers armed with farm tools and shotguns confronted the militia and refused to leave. Curtis eventually sold the land grant in parcels of mostly 150 to 500 acres (60-200 ha) through the early 1860s.

In northern California and southern Oregon where surface water is often minimal during the summer, juvenile salmon depend on groundwater aquifers to sustain their tributary habitats. Fishing, logging, land clearing and development, channel clearing and modification, stream diversions, water extractions, and water pollution have altered the quantity, quality, and timing of in-stream flows, limiting the habitat for steelhead and coho salmon which were once abundant in Salmon Creek and its tributaries. Throughout the 1950s, fish were relatively abundant in the watershed. By the early 1980s, coho fry were reportedly being stocked in Salmon Creek and regular fish surveys were started.
Coho salmon were observed on a regular basis in the late 1980s through early to mid-1990s. In 1996, the last wild coho salmon was seen in the watershed. Ongoing survey work since that time has documented steelhead but no wild coho salmon have been observed and they are believed to be extirpated from the watershed. As a result, these species are now protected under the federal and State Endangered Species Acts. Read more here and here. Explore more of Salmon Creek and Sonoma Coast State Park here: