Stock Island is an island in the lower Florida Keys immediately east of Key West (separated from Key West by Cow Key Channel, which is only about 75 yards (70 m) wide). Immediately northwest is Key Haven (official name Raccoon Key), from which it is connected by causeway with US 1 (the Overseas Highway). The part north of U.S. 1 is part of the City of Key West, while the southern part is a census-designated place (CDP) in Monroe County, Florida, United States. The population of the CDP was 4,410 at the 2000 census. Stock Island was supposedly named for herds of livestock formerly kept there. Alternatively, some local historians suggest that it may be named for an early settler.