Marshall is an unincorporated community in Marin County, California. It is located on the northeast shore of Tomales Bay 6 miles (9.7 km) south of Tomales, at an elevation of 23 feet (7 m).Marshall is located on the east shore of Tomales Bay. It has a population of about 400, although it has long claimed a population of 50 and touted this as the sum of the elevation (15 feet or 4.5 m above sea level) and the speed limit of 35 miles per hour (56 km/h).