Its' the first island of the coast of Cape Cod, Massachusetts right next to Nantucket. I go there every summer. Answer II Martha's Vineyard is an island in Massachusetts, to the south of Cape Cod.
The population of Martha's Vineyard on December 15th 2011 is approximately 19,138,617. (Extrapolated from a population of 15,000 on June 25th 2009 and a population of 16,500,877 on August 10th 2011.)