A Geography Measured in Extremes
The United States, considered geographically, extends far beyond the contiguous 48 states. It includes Alaska, Hawaii, Washington, D.C., five populated territories, and several minor outlying possessions. Its borders include the world’s longest bi-national land boundary, shared with Canada, as well as a southern border with Mexico and maritime boundaries near Russia, Cuba, and the Bahamas.
The country’s size and shape produce extraordinary physical diversity. Eight major physiographic divisions organize the continental landscape, from the Laurentian Upland and Atlantic Plain to the Appalachian Highlands, Interior Plains, Rocky Mountain System, Intermontane Plateaus, and Pacific Mountain System. These regions contain Great Lakes shorelines, forests, grasslands, farmland, cave systems, deserts, volcanic ranges, deep gorges, and coastal islands. The highest point is Denali in Alaska; the lowest is Death Valley in California.
Nearly every major climate appears somewhere in the United States. Alaska has polar conditions, Hawaii and southern Florida are tropical, California’s coast has a Mediterranean climate, the Great Plains can be semiarid, and the Southwest is arid desert. The polar jet stream, Gulf of Mexico moisture, mountain ranges, and large bodies of water help create blizzards, thunderstorms, lake-effect snow, heat waves, and rapid temperature changes.
Natural hazards are equally varied. Tornado Alley experiences frequent tornadoes, Atlantic and Gulf coasts face hurricanes, the West endures earthquakes, volcanoes, drought, and wildfire, and many regions experience flooding. The Dust Bowl demonstrated how drought can transform both land and society.
National parks, forests, wilderness areas, and other public lands preserve and expose this immense geographic variety.