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. The creek is named after historical runs of steelhead trout and coho salmon. It has no impoundment dams, although there are 43 active water diversions for domestic and agricultural supply. The watershed is characterized by scattered rural development amid pasture, vineyards, and mixed hardwood and redwood forest. The upper watershed is underlain by rocks of the Wilson Grove Formation, which developed during the late Miocene to late Pliocene (about 12 million to 3 million years ago) and consists of unconsolidated fine-grained sand with minor amounts of gravel and tuff deposited under beach and shallow-marine conditions. The formation overlies the Franciscan Complex, exposed along the coast, which consists of graywacke sandstones, shales, and conglomerates that developed between the late Cretaceous to Eocene (about 75 million to 34 million years ago) and 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 its northern settlements in Alaska while continuing trade with the Franciscan missions of Spanish Alta California. After Mexican 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 Russian expansion, the government issued land grants to prominent citizens and military veterans. In 1844 Governor Manuel Micheltorena gave Captain Stephen Smith a land grant of 35,487 acres (14,361 ha) named Rancho Bodega. 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 along Salmon Creek. He died in 1855; his widow, Manuela Torres, later married Tyler Curtis. When Mexico ceded Alta California to the United States in 1848, Curtis received the land patent for Rancho Bodega. He attempted to evict squatters and settlers farming parcels on the rancho and hired an enforcement militia of about 40 men in what became known as the Bodega War. Around 200 settlers armed with farm tools and shotguns confronted the militia and refused to leave. Curtis eventually sold the grant in parcels of mostly 150 to 500 acres (60–200 ha) through the early 1860s.

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