The Estero Americano is a coastal estuary at the base of Americano Creek; the watershed area is 49 square miles. It forms a portion of the northern boundary between Marin and Sonoma counties where it drains into Bodega Bay. In some years, a seasonal sand bar at the mouth restricts tidal exchange. Periods of hypersalinity have been recorded in the Estero. When the mouth is open, the tidal influence ranges up to 4 miles upstream. Americano Creek, the sole tributary of the Estero, is ephemeral and generally dries up for 4 to 6 months between late spring and fall.
Historically, the watershed was inhabited by Coast Miwok. From 1865 to 1982, the area was used extensively for agriculture, including corn, beets, potatoes, onions, oats, and hay. In the late 1800s, the Estero Americano was reportedly a navigable body of water, and products such as potatoes were shipped to market.
Learn more about the watershed habitat and land use.