San Nicolas Island is the most remote of California's Channel Islands. It is part of Ventura County. The 14,562 acre (58.93 km² or 22.753 sq mi) island is currently controlled by the United States Navy and is used as a weapons testing and training facility, served by Naval Outlying Field San Nicolas Island. The uninhabited island is defined by the United States Census Bureau as Block Group 9, Census Tract 36.04 of Ventura County, California. The Nicoleño Native American tribe inhabited the island until 1835. As of the 2000 U.S. Census, the island has since remained officially uninhabited, though the census estimates that at least 200 military and civilian personnel live on the island at any given time.