Oroville (formerly, Ophir City) is the county seat of Butte County, California. The population was 13,004 at the 2000 census, and it is one of the faster growing towns in California, with an 11.9% increase in population from 2000 to June 2007. The national average population increase is less than one percent. The Berry Creek Rancheria of Maidu Indians of California is headquartered here.