Chatham is a town in Barnstable County, Massachusetts, United States, Barnstable County being coextensive with Cape Cod. First settled by the English in 1664, the township was originally called Monomoit based on the indigenous population's term for the region. The population was 6,125 at the 2010 census. Chatham is home to the Monomoy National Wildlife Refuge, located on Monomoy Island,