Plumas County is a county located in the Sierra Nevada of the U.S. state of California. As of the 2010 census, the population was 20,007. The county seat is Quincy, and the only incorporated city is Portola. The largest community in the county is East Quincy. The county gets its name from the Spanish words for the Feather River (Río de las Plumas), which flows through the county.
Plumas County is located in the far northern end of the Sierra Nevada range. The area’s rugged terrain marks the transition point between the northern Sierra Nevadas and the southern end of the Cascade Range. Lassen Peak, which is the southernmost volcanic peak in the Cascade Range, is found just north of Plumas County’s border, and part of Lassen Volcanic National Park extends into the northwest corner of the county.