Modoc County is a county located in the far northeast corner of the U.S. state of California, bounded by the state of Oregon to the north and the state of Nevada to the east. As of the 2010 census, its population was 9,686, up from 9,449 at the 2000 census. The current county seat is Alturas, the county's only incorporated city. Previous county seats include Lake City and Centerville; the latter is now a ghost town. The county's official slogans include, "The last best place," and "Where the West still lives."
A large portion of Modoc County is federal land. Several federal agencies, including the United States Forest Service, Bureau of Land Management, National Park Service, Bureau of Indian Affairs, and the United States Fish and Wildlife Service, have employees assigned to the area, and their operations are a significant part of the economy and services in this rural area.
Modoc County is the only county in California to be bordered by both Nevada and Oregon, and is also one of three counties in California to border more than one state (the other counties being San Bernardino County, bordered by Nevada and Arizona; and Imperial County which borders Arizona and Baja California in Mexico). In California, this is the only almost rectangular county; there is a slight deviation around the Tule Lake National Wildlife Refuge.