Alpine County is a county located in the Sierra Nevada region of California. As of the 2010 census, the population was 1,175, making it the least populous county in California. The largest community is Markleeville. There are no incorporated cities in the county. The county borders El Dorado County to the north, the state of Nevada to the northeast, Mono County to the east, Tuolumne County to the south, and Amador County to the west.