United States: Physical Geography

The United States is the world's third- or fourth-largest country by total area, covering nearly 9.9 million square kilometers across North America. The contiguous 48 states lie between Canada to the north and Mexico to the south, bordered by the Atlantic Ocean, the Gulf of Mexico, and the Pacific Ocean, while Alaska occupies the continent's northwestern corner and Hawaii lies far offshore in the central Pacific. Geologists traditionally divide the continental United States into several major physiographic regions, and the country's relief broadly reflects a pattern in which the Atlantic coast is low-lying while the Pacific coast is comparatively mountainous.

East of the Mississippi River, a broad, low coastal plain extends along the Atlantic and Gulf shores from New York to Texas, giving way inland to the Appalachian Highlands, a long chain of relatively low, ancient mountains separating the eastern seaboard from the interior. West of the Appalachians lies the vast Central Lowland of the Mississippi River basin, fed by the Ohio and Tennessee rivers, bordered to the south by the Ozark Plateau and Ouachita Mountains, the chief uplands between the Appalachians and the Rockies. The five Great Lakes line the northern border with Canada, and the Great Plains rise gradually from the Mississippi valley westward toward the Rocky Mountains.

The Rocky Mountains, the eastern branch of the Cordilleran system that dominates the West, reach their highest points in Colorado. Beyond them lie the arid Intermontane Plateaus, including the Colorado Plateau, home to the Grand Canyon, and the Great Basin, a region of isolated ranges and closed drainage basins. The Cascade Range and Sierra Nevada form the Pacific Mountain System near the west coast; within the Sierra Nevada lies Mount Whitney, the highest point in the contiguous states, just over 130 kilometers from Badwater Basin in Death Valley, the lowest point in North America. Farther northwest, Alaska holds Denali, the continent's highest peak, while Hawaii, in the central Pacific, consists of volcanic islands.