Lummi Island lies at the southwest corner of Whatcom County, Washington, USA, between the mainland part of the county and offshore San Juan County. The Lummi Indian Reservation is situated on a peninsula east of the island, but does not include Lummi Island. The island has a land area of 23.97 km² (9.255 sq mi) and had a population of 822 as of the 2000 census. The population nearly doubles in summer when property owners from both Canada and the U.S.