barrier island off the Atlantic coast of southeastern Maryland and eastern Virginia, U.S. Established as a national seashore in 1965, it is 37 miles (60 km) long, occupies 62 square miles (160 square km), about half land and half water, and is separated from the mainland by Chincoteague Bay, which is spanned by two bridges—one from Sinepuxent, Md., near the northern end, and the other from Chincoteague, Va., near the southern tip. The famous wild horses (Chincoteague “ponies,” which are rounded up each July for auction), deer, small mammals, and waterfowl thrive in the pinelands and marshes of the Chincoteague National Wildlife Refuge at the southern end of the island. The refuge is also a bird sanctuary on the Atlantic Flyway. In sheltered bays and inlets, oysters and clams are harvested.