Mill Valley is a city in Marin County, California, United States located about 4 miles (6.4 km) north of San Francisco via the Golden Gate Bridge. According to the United States Census Bureau, the city has a total area of 12.5 km² (4.8 mi²). 12.2 km² (4.7 mi²) of it is land and 0.3 km² (0.1 mi²) of it (2.28%) is water. Mill Valley is located on the western and northern shores of Richardson Bay, fed by Pickleweed Inlet and Arroyo Corte Madera del Presidio which traverse through Mill Valley. Beyond the flat coastal area and marshlands, it occupies narrow wooded canyons, mostly of second-growth redwoods, on the eastern slopes of Mount Tamalpais.