Oroville (formerly, Ophir City) is the county seat of Butte County, California. The population was 15,506 (2010 census), up from 13,004 (2000 census). Oroville is located off of Highway 70, and is in close proximity to Highway 99, which connects Butte County with Interstate 5. Chico, California is located about 25 minutes north of the city, and Sacramento lies about an hour south. Oroville is considered the gateway to Lake Oroville and Feather River recreational areas.The Berry Creek Rancheria of Maidu Indians of California is headquartered here. The City of Oroville has recently annexed two location in South Oroville, areas A and B, which have a combined population of 2,725 people. The U.S. Census Bureau estimated the population of the city to be 17,996 as of Jan. 1, 2016, up 1,908 people or 11.9 percent during 2015.