Chatham is a town in Barnstable County, Massachusetts, United States. Chatham is located at the southeast tip of Cape Cod, and has historically been a fishing community. First settled by the English in 1664, the township was originally called Monomoit based on the indigenous population's term for the region. Chatham was incorporated as a town on June 11, 1712, and has become a summer resort area. The population was 6,169 at the 2017 census, and can swell to 25,000 during the summer months. There are four villages that comprise the town, those being Chatham (CDC), South Chatham, North Chatham, and West Chatham. Chatham is home to the Monomoy National Wildlife Refuge, and the decommissioned Monomoy Point Light both located on Monomoy Island. A popular attraction is the Chatham Light, which is an operational lighthouse that is operated by the United States Coast Guard.
The town occupies the southeast corner (the "elbow") of Cape Cod. The town's villages include Chatham proper, Chatham Port, North Chatham, West Chatham, and South Chatham (west of West Chatham). Chatham is bordered by Harwich to the west, Pleasant Bay and Orleans to the north, the Atlantic Ocean to the east, and Nantucket Sound to the south. The town is 35 miles (56 km) south of Provincetown and east of the Sagamore Bridge, 20 miles (32 km) east of Barnstable, and 85 miles (137 km) southeast of Boston.
According to the United States Census Bureau, the town has a total area of 24.4 square miles (63.2 km2), of which 16.1 square miles (41.8 km2) is land and 8.3 square miles (21.4 km2), or 33.88%, is water.
The mainland portion of the town is typical of Cape Cod, with several ponds, brooks, rivers, harbors, and inlets around the town. The town includes two narrow strips of land which serve as a barrier between the Atlantic and the mainland; the northern of these is the southern part of the Cape Cod National Seashore. There are several islands, including Strong Island, Tern Island (which is a sanctuary), Morris Island, Stage Island, and Monomoy Island, a 7.25-mile-long (11.67 km) island south of the corner of the town which is home to the Monomoy National Wildlife Refuge. Erosion has changed the region over the years—for example, an island named Slut's Bush once existed until it vanished under water by the mid 19th century.