| Estero de San Antonio | |
| Name Other: | San Antonio Creek |
| Name Etymology: | Spanish Saint Anthony's Estuary |
| Pushpin Map: | USA California |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of the mouth of Estero de San Antonio in California |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | California |
| Subdivision Type3: | Region |
| Subdivision Name3: | Marin and Sonoma counties |
| Length: | 9.5miles |
| Source1 Location: | 1.51NaN1 southwest of Bloomfield, California |
| Source1 Coordinates: | 38.3031°N -122.8769°W |
| Source1 Elevation: | 400feet |
| Mouth: | Bodega Bay |
| Mouth Coordinates: | 38.27°N -122.9794°W |
| Mouth Elevation: | 0feet |
| Basin Size: | 50sqmi[1] |
| Tributaries Left: | Stemple Creek |
Estero de San Antonio is a stream in the northern California counties of Marin and Sonoma which empties into Bodega Bay.
The Estero springs just north of the Marin-Sonoma county line (from a hill overlooking Bloomfield, California) and runs south along Gericke Road into Marin County. Just north of Fallon-Two Rock Road, it turns west, flowing under the road just east of State Route 1. It flows south along the highway for 0.251NaN1, then crosses under the highway at milepost 47.6 and continues west to a confluence with Stemple Creek 0.31NaN1 southeast of Fallon, California. From there, it winds its way westward, passing under Middle Road and Valley Ford Franklin School Road before emptying into Bodega Bay 1.51NaN1 north of Dillon Beach, California.
The Estero de San Antonio has a variety of habitat types, including freshwater ponds, mudflats, eelgrass and saltgrass area, and wooded ravines. It is estimated that the Estero has 9230NaN0 of associated wetlands.[2]
In the summer or early fall, a sandbar often forms at the mouth of the Estero, damming it until the winter rains arrive. Area residents used to blast the sandbar to dispel high salt concentrations in the Estero.[1]
The United States Geological Survey's Geographic Names Information System cites ten variant names for this stream, including Stemple Creek (the name of its main tributary), Estero De Americano (almost identical to the parallel estuary 20NaN0 north), Arroyo de San Antonio (also applied to Walker Creek, a parallel estuary 50NaN0 south), and San Antonio Creek (the name of a creek further east along the county line). In particular, the Estero's watershed is often referred to as the Stemple Creek watershed.[3] The stream is also referred to as Fallon Creek.
The Estero de San Antonio is crossed by three concrete continuous slab bridges:
It is also crossed at Fallon-Two Rock Road by a 220NaN0 concrete tee beam bridge built in 1932.[4]