Nantucket is an island  south of Cape Cod, in the American state of Massachusetts. Together with the small islands of Tuckernuck and Muskeget, it constitutes the Town of Nantucket, and the conterminous Nantucket County, which are consolidated. As of the 2010 census, the population was 10,172, making it the least-populous county in Massachusetts. Part of the town is designated the Nantucket CDP, or census-designated place. The region of Surfside on Nantucket is the southernmost settlement in Massachusetts.