3. Interior Lowlands

Moving eastward from the Rocky Mountains and stretching to the Appalachians is a huge area of lowland plains. The west­ern portion, the Great Plains, lies west of a line that roughly coincides with the 100th meridian and includes portions of Texas, New Mexico, Colorado, Wyoming, North and South Dakota, and Montana. On the western margin (where Denver, Colorado, calls itself the “Mile High City”), they reach an elevation of more than 5,200 feet (1,585 meters). Eastward, the plains drop very gradually in elevation until they reach the Missouri and Mississippi rivers. Generally flat terrain is broken in places by isolated buttes, mesas, and low mountains such as South Dakota’s Black Hills, site of America’s famous “shrine to democracy,” Mount Rushmore. The highest peak in the Black Hills, 7,242-foot (2,207-meter) Harney Peak, is also the highest point in Northern America east of the Rocky Mountains.

East of the Great Plains and extending across the Missis­sippi River basin to the foothills of the Appalachians is a region variously called the Central or Interior Lowlands or Plains. The area extends from north-central Texas to the eastern Dakotas and eastward to Ohio and Michigan. The region coincides with America’s “breadbasket.” Excellent soils, ample moisture, and large expanses of flat land that allow the use of heavy equipment help make this region one of the world’s most productive agricultural areas.

4. Appalachian Mountains

The Appalachians are an ancient system of low mountains that extend from Alabama to New England (and into eastern Can­ada). This unique land form is the result of geologic folding. Millions of years ago, forces that worked from within the earth pushed toward one another, creating a ripple-like landscape. The mountains are relatively low, reaching their highest elevation of 6,684 feet (2,037 meters) atop Mount Mitchell in western North Carolina. Initially, the Appalachians formed a divide between the eastern seaboard and the country’s interior. As the land was forced upward, however, ancient rivers scoured narrow east-west–trending valleys called “gaps.” These passageways, such as the famous Cumberland Gap, located at the point where Kentucky, Tennessee, and Virginia meet, created corridors followed by early Amerindians, European pioneers, and, later, railways and highways.

5. Piedmont and Atlantic and Gulf Coastal Plains

Immediately to the east of the Appalachians is a hilly upland area that gradually drops toward the coastal plain. Its name comes from its location: pied (foot) and mont (mountain). At the point where the Piedmont and the coastal plain join is a narrow strip called the “fall zone” or “fall line.” The name, of course, comes from falls or rapids that occur along streams that flow eastward from the mountains. These areas became important points for early settlement.

Rapidly flowing water provided an ideal site for water-powered saw, flour, and other industrial mills. It also marked the head of navigation on streams that flowed from the mountains to the Atlantic Ocean. Goods being transported by water had to be placed on land-based vehicles (and vice versa) in a process called “break in bulk.” Warehouses often developed around such sites to take advantage of the need for storage. Lively trade and commerce also are associated with such locations. Nearly 30 cities were founded and grew as a result of the many advantages offered by the fall zone (line). They include Philadelphia; Baltimore; Washington, D.C.; Richmond, Virginia; Raleigh, North Carolina; Columbia, South Carolina; Augusta, Georgia; and Tuscaloosa, Alabama.

A low-lying, flat-to-gently-rolling coastal plain extends from New Jersey to Texas. Regionally, it is divided into the Atlantic and Gulf coastal plains. The Atlantic portion extends from the mouth of New York’s Hudson River to eastern Florida. The Gulf coastal plain includes an arc that extends from western Florida to southern Texas. Along the coast, thriving urban centers such as Boston, Massachusetts; New York City; Tampa, Florida; and the Galveston Bay area of Texas all developed as seaports. Ample freshwater, fertile soils, woodlands, and access to the sea combined to make this region attractive to early settlers.