High Quality Content by WIKIPEDIA articles! Vashon is a census-designated place (CDP) in King County, Washington, United States. It covers an island alternately called Vashon Island or Vashon-Maury Island, the largest island in Puget Sound south of Admiralty Inlet. The population was 10,624 at the 2010 census. At 37 square miles (96 km2), it is about 60 percent larger in area than Manhattan, with about 1/150 the population. There are no bridges to connect the island with the mainland, a big factor contributing to the island`s relative isolation and rural character.