Plumas County is located in the Sierra Nevada of the U.S. state of California. The county gets its name from the Spanish words for the Feather River (Río de las Plumas), which flows through the county.The county seat is Quincy. The only incorported city in the county is Portola. The county has a total area of 2,613 mi², 98% of it is land and 2% of it is water. As of the census of 2000, there were 20,824 people, 9,000 households, and 6,047 families residing in the county. The population density was 8/mi².