Key West is a city in Monroe County, Florida, United States. The city encompasses the island of Key West, the part of Stock Island north of U.S. 1 (the Overseas Highway) (east), Sigsbee Park (north, originally known as Dredgers Key), Fleming Key (north), and Sunset Key (west, originally known as Tank Island). Both Fleming Key and Sigsbee Park are part of Naval Air Station Key West and are inaccessible by civilians. Key West is the county seat of Monroe County. Key West is the southernmost city in the Continental United States. It also contains the southern terminus of U.S.