Plumas County was created in 1854 from Butte County. The Spanish originally called one of the tributaries of the Sacramento River El Rio de las Plumas or the "River of Feathers." In creating this county, the state Legislature gave it the name Plumas because all of the numerous branches of the Feather River have their origins in its mountains. Territory which at one time was in Plumas County is now in Lassen, Shasta, and Sierra Counties.

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