Chatham is a town in Barnstable County, Massachusetts, United States, Barnstable County being coextensive with Cape Cod. Chatham is home to the Monomoy National Wildlife Refuge, located on Monomoy, and to Monomoy Theatre. Chatham is home to the Chatham Lighthouse, which was established by President Thomas Jefferson in 1808 to protect the ships circling the Cape. Originally consisting of two lights, the pair were moved back and rebuilt in 1877. The second was moved to Eastham to become the Nauset Light in 1923, after both were upgraded to rotating lights. Today, the keeper's house is home to a Coast Guard station which tends the light.