North Carolina consists of three main geographic sections: the Atlantic Coastal Plain, which occupies the eastern 45% of the state; the Piedmont region, which contains the middle 35%; and the Appalachian Mountains and foothills. The extreme eastern section of the state contains the Outer Banks, a string of sandy, narrow barrier islands between the Atlantic Ocean and two inland waterways or "sounds": Albemarle Sound in the north and Pamlico Sound in the south. They are the two largest landlocked sounds in the United States.