The United States is the world's fourth largest country, with an area of 3,679,192 square miles (9,529,107 square kilometers). It includes fifty states and one federal district, where the capital, Washington, D.C., is located. Its forty-eight contiguous states are situated in the middle of North America. The mainland United States borders Canada to the north and Mexico, the Gulf of Mexico, and the Straits of Florida to the south. The western border meets the Pacific Ocean, and to the east lies the Atlantic Ocean.
Alaska and Hawaii are not joined to the other forty-eight states. Alaska is at the extreme north of North America, between the Pacific and Arctic oceans, and is bordered by Canada to the east. The island chain of Hawaii is situated in the east-central Pacific Ocean, about two thousand miles southwest of San Francisco.
Although Americans generally do not consider themselves an imperial or colonial power, the country has a number of commonwealths and territories, most of which were acquired through military conquest. These territories include Puerto Rico and the Virgin Islands in the Caribbean basin, and Guam, the Northern Mariana Islands, American Samoa, and Wake island in the Pacific.
The physical environment is extremely diverse and often spectacular. Alaska's glaciers coexist with flowering tundras that bloom in the arctic summer. The forests of the Pacific Northwest and northern California are known for giant ancient trees such as Sitka spruce and sequoia (redwoods). Niagara Falls, Yellowstone National Park, and the Grand Canyon are a few of the better-known landscapes.
The physical regions of the country overlap both national boundaries and cultural regions. For example, the Atlantic coastal plain extends from New England to Mexico's Yucatan Peninsula. It is characterized by flooded river valleys that form major estuaries, such as the Chesapeake Bay.
The United States of America (commonly referred to as the United States, the U.S., the USA, or America) is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its 48 contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to its east and Russia to the west across the Bering Strait. The state of Hawaii is an archipelago in the mid-Pacific. The country also possesses several territories, or insular areas, in the Caribbean and Pacific.
The nation was founded by thirteen colonies of Great Britain located along the Atlantic seaboard. On July 4, 1776, they issued the Declaration of Independence, which proclaimed their independence from Great Britain and their formation of a cooperative union. The rebellious states defeated Great Britain in the American Revolutionary War, the first successful colonial war of independence. The Philadelphia Convention adopted the current United States Constitution on September 17, 1787; its ratification the following year made the states part of a single republic with a strong central government. The Bill of Rights, comprising ten constitutional amendments guaranteeing many fundamental civil rights and freedoms, was ratified in 1791.Geography
The contiguous United States (the 48 states other than Alaska and Hawaii) are bounded by the Atlantic Ocean to the east and the Pacific Ocean to the west, with much of the population living on these two coasts. Its only borders are shared with Canada to the north, and Mexico to the south.
The country has three major mountain ranges. The Appalachians extend from Canada to the state of Alabama, a few hundred miles west of the Atlantic Ocean. They are the oldest of the three mountain ranges, and offer spectacular sightseeing and excellent camping spots. The Rockies are the highest in North America, extending from Alaska to New Mexico, with many areas protected as national parks. They offer hiking, camping, and sightseeing opportunities. The combined Sierra Nevada and Cascade ranges are the youngest. The Sierras extend across the "backbone" of California, with sites such as Lake Tahoe and Yosemite National Park, then give way to the even younger volcanic Cascade range, with some of the highest points in the country.
The Great Lakes define much of the border between the United States and Canada. Formed by the pressure of glaciers retreating north at the end of the last Ice Age, the five lakes touch the states of Minnesota, Wisconsin, Illinois, Indiana, Michigan, Ohio, Pennsylvania and New York. The lakes span hundreds of miles, and their shores vary from pristine wilderness areas to industrial "rust belt"cities. They are the second-largest bodies of freshwater in the world, after the polar ice caps.Climate
The overall climate is temperate, with notable exceptions. Alaska has Arctic tundra, while Hawaii and South Florida are tropical. The Great Plains are dry, flat and grassy, turning into arid desert in the far West and Mediterranean along the California coast.
In the winter, the northern and mid-western major cities can see as much as 2 feet (61 cm) of snow can fall in one day, with cold temperatures. Summers are humid, but mild. Temperatures over 100F (38C) sometimes invade the Midwest and Great Plains. Some areas in the northern plains can experience cold temperatures of-30F(-34C) during the winter. Temperatures below 0F(-18C) sometimes reach as far south as Oklahoma.
The climate of the South also varies. In the summer, it is hot and humid, but from October through April the weather can range from 60F (15C) to short cold spells of 20F(-7C) or so.