Fairfax is an incorporated town in Marin County, California, United States. Take a look below for 10 interesting and amazing facts about Fairfax, California, United States. 1. Fairfax is located 3.25 miles (5.2 km) west-northwest of San Rafael, at an elevation of 115 feet (35 m). 2. The population was 7,441 at the 2010 census….