Cape Cod, often referred to locally as simply the Cape, is a cape in the easternmost portion of the state of Massachusetts, in the Northeastern United States. Today it is co-extensive with Barnstable County, and is defined by the towns along the Cape Cod Canal, and those to the east on the peninsula all the way to Provincetown. Several small islands right off Cape Cod, including Monomoy Island, Monomoscoy Island, Popponesset Island, and Seconsett Island, are also in Barnstable County, being part of municipalities with land on the Cape. The Cape's historic and maritime character and ample beaches attract heavy tourism during the summer months.

Cape Cod was formed as the recessional moraine of a glacier, resulting in a peninsula in the Atlantic Ocean.

In 1914, the Cape Cod Canal was cut through the base or isthmus of the peninsula, forming what may be loosely described as an island. The Cape Cod Commission refers to the resultant landmass as an island; as does the Federal Emergency Management Agency (FEMA) in regards to disaster preparedness.[1]
Cape Cod is one of the biggest barrier islands in the world, shielding much of the Massachusetts coastline from North Atlantic storm waves. This protection erodes the Cape's shoreline at the expense of cliffs, while protecting towns from Fairhaven to Marshfield - Source Wikipedia