A Continent in Eight Acts
The continental United States is organized into eight broad physiographic divisions—large regions shaped by shared landforms and geological history.
The Laurentian Upland extends the ancient Canadian Shield into the Great Lakes region. Along the Atlantic and Gulf coasts, the Atlantic Plain forms a broad, generally low landscape of beaches, barrier islands, wetlands, and continental shelf.
The Appalachian Highlands occupy the East. Their mountains are relatively old and worn down, but they still separate the eastern seaboard from the Great Lakes and Mississippi basins. The region includes the Appalachians, Adirondacks, Watchung Mountains, and New England landscapes.
The Interior Plains stretch between the Mississippi River and Rocky Mountains. They include the Great Plains, agricultural heartlands, badlands, painted hills, and extensive cave systems. Nearby, the Interior Highlands—including the Ozarks and Ouachitas—form the major mountainous region between the Appalachians and Rockies.
The Rocky Mountain System rises through the West. Its ranges are broken by basins and valleys rather than forming one continuous wall. Colorado’s Mount Elbert is its highest peak.
West of the Rockies, the Intermontane Plateaus contain the Columbia and Colorado plateaus and the Basin and Range Province. This is the setting of the Great Basin, Death Valley, and Grand Canyon.
Finally, the Pacific Mountain System forms the mountainous western margin, including the Cascades, Sierra Nevada, and coastal ranges.
Together, these divisions explain why the United States contains such sharply contrasting scenery: low coasts, rolling plains, ancient mountains, high plateaus, deep canyons, and rugged volcanic peaks.