The United States (U.S.) consists of the Continental U.S. (48 states and the District of Columbia), and the satellite states of Alaska and Hawaii. The U.S. is the fourth largest country in the world, encompassing approximately 3,717,810 square miles (9,629,091 square kilometers). Of that, 181,517 square miles (470,131 square kilometers) are covered with water. The country's highest point is Mount McKinley in Alaska, which is 20,319 feet (6,194 meters) above sea level. California's Death Valley is the lowest point at 282 feet (86 meters) below sea level.

The Continental U.S.
The Continental U.S. is bordered by Canada to the north and Mexico to the south. The Atlantic Ocean is to the east and to the west is the Pacific Ocean. The Continental U.S. can be divided roughly in to three regions, the Eastern Region, Central Region and Western Region. The Eastern region spans from approximately the Atlantic Ocean to the Appalachian Mountain Range. The Central Region covers the area between the Appalachian Mountains and the Rocky Mountains and from the Rocky Mountains to the Pacific Ocean is the Western Region.

The Eastern Region
In the northern portion of this region are the Great Lakes: Erie, Huron, Michigan, Ontario and Superior. Lake Superior is the furthest inland in this chain of lakes, which run through eight states. The Lakes contain some six quadrillion gallons of fresh water, which is one-fifth of the world's fresh surface water, and cover approximately 94,000 square miles (244,000 square kilometers) of area. Located between Lake Erie and Lake Ontario is Niagara Falls. They are the second largest waterfalls in the world and consist of the American Falls/Bridal Veil Falls and Horseshoe Falls (located in Canada). The American Falls/Bridal Veil Falls move 150,000 U.S. gallons (567,811 liters) of water per second while Horseshoe Falls move 600,000 U.S. gallons (2,271,247 liters).

The Appalachian Mountain Range begins in Quebec, Canada and extends from Maine to Georgia in the United States. The Appalachians are among the oldest mountains on Earth and are divided into parallel chains that include the Allegheny, the Blue Ridge and Catskill Mountains. The highest peaks in this Mountain Range are located in the Great Smoky Mountains National Park (North Carolina and Tennessee).

Everglades National Park is located in Florida, the most southern state. The Everglades are formed by a fresh water river, which is only six inches (15 centimeters) deep and 50 miles (80 kilometers) wide. The river flows slowly across the flat expanse of land at the southern tip of the state.

The Central Region
Inland from the Appalachians in Kentucky is Mammoth Cave National Park. Over millions of years, the area's extensive cave system has developed into the world's largest, with more than 348 miles (560 kilometers) explored and mapped. Taking up the largest portion of the Central Region are the Great Plains. Here, Tallgrass Prairie located in the east changes to Shortgrass Prairie in the west until reaching the foothills of the Rocky Mountains. The Great Plains extend from Canada in the north to Texas in the south. Isolated mountainous regions such as the Ozarks can be found throughout, the Central Region

The Western Region
Along the interior portion of the Western Region are the Rocky Mountains, which are a younger and more rugged version of the Appalachian Mountain Range. The Rockies begin in Northern Canada and extend as far south as New Mexico. The Continental Divide is a ridge of high ground that runs irregularly north and south through the Rocky Mountains. It separates eastward and westward flowing streams - water that flows westward empties into the Pacific Ocean, while the water flowing eastward is deposited in the Atlantic Ocean via the Gulf of Mexico.

In Montana, where the Rockies cross the Canadian border, is Waterton-Glacier International Peace Park. Some of its mountain peaks exceed 10,000 feet (3,048 meters) and there are dozens of glaciers, as well as many lakes and streams. Following the Rockies south, Yellowstone National Park is home to hot springs, geysers, lava formations, lakes, waterfalls, rivers and river canyons.

Further south in Arizona is Grand Canyon National Park. This area consists of plateaus, mesas and deep canyons including the Grand Canyon. The Grand Canyon is 6000 vertical feet (1829m) at its deepest point and covers an area of 1,904 square miles (4937 sq. km).

Westward from the Grand Canyon, toward the Pacific Coast, is the Basin and Range. Here, the earth’s crust stretched until it thinned and eventually cracked, creating large faults. Along these faults, mountains lifted up and valleys dropped down, producing the distinctive alternating pattern of linear mountain ranges and valleys. Yosemite National Park is found within this region. It harbors a collection of waterfalls, meadows and forests that include groves of giant sequoias.

On the western coast of Continental U.S. is the Pacific Mountain System. This area is one of the most geologically young and tectonically active in North America. Redwood National Park, which contains the tallest living things on earth - evergreen trees that grow to be 350 feet (106 meters) - is located in this region. North toward the Canadian border is Olympic National Park, which encompasses three completely different ecosystems: glacier capped mountains, untouched Pacific coast and temperate rain forest.

Alaska
Alaska is located on the northernmost portion of the North America, just west of Canada's Yukon Territory. Much of Southeastern Alaska is mountainous with glaciers and inlets, while the Alaskan Peninsula and Aleutian Islands form an arc of more than 75 volcanoes. Interior Alaska is the drainage basin of the state's main river, the Yukon. Located on the border between Alaska and Canada are Wrangell-St. Elias National Park & Preserve and Glacier Bay National Park, both of which contain huge chains of glaciers. These enormous ice sheets continue to move, shaping and transforming the landscape.

Hawaii
Hawaii is located west of Continental U.S. in the Pacific Ocean. The state consists of five principal islands as well as four smaller ones. The Hawaiian Islands are volcanic formations of basaltic lava flows. The terrain is hilly and the coastlines are mostly rocky and rough. Hawaii Volcanoes National Park is home to several active volcanoes.