The
Atlantic Plain is one of eight distinct
United States physiographic regions. This major division consists of the
Continental Shelf and
Coastal Plain physiographic provinces. It is the flattest of the U.S. physiographic divisions and stretches over in length from
Cape Cod to the
Mexican border and southward another to the
Yucatán Peninsula. The central and southern
Atlantic Coast is characterized by barrier and drowned valley coasts. The coastal Atlantic plain features nearly continuous barriers interrupted by
inlets, large
embayments with drowned river valleys, and extensive
wetlands and
marshes. The Atlantic plain slopes gently seaward from the inland highlands in a series of terraces. This gentle slope continues far into the Atlantic and
Gulf of Mexico, forming the continental shelf. The relief at the land-sea interface is so low that the boundary between them is often blurry and indistinct, especially along stretches of the Louisiana bayous and the
Florida Everglades.