The United States of America is the third largest country in the world, with coastlines on both the Atlantic Ocean and the Pacific Ocean and borders with Canada to the north and Mexico to the south. Due to its vast size, it has many diverse landscapes, climatic conditions, and cultural traditions. Geographically, the mainland (excluding Hawaii and Alaska) consists of a vast central plain, with mountains to the west and hills and low mountains in the east. Mainland USA is commonly referred to as the “the contiguous 48” or “the lower 48,” meaning the 48 States that lie between Canada and Mexico.

The capital of the USA, and seat of government, is Washington, D.C. (formally, the District of Columbia). Washington, D.C. is often simply called Washington and can therefore be confused with the state of Washington; for this reason, most people refer to the state of Washington as Washington State. Washington, D.C. is not a state on its own, nor is it part of a state; instead, it is a separate municipality nestled between the states of Virginia and Maryland.

The largest cities in the United States include New York City, Los Angeles, Chicago, Houston, and Philadelphia. In contrast to the crowded, bustling cities with their high-rise modern buildings, much of rural America has a fairly low population density; agriculture is still an important form of economic activity, and traditional social norms and values are still very strong.

The USA also holds several overseas territories. These include Puerto Rico, the US Virgin Islands, American Samoa, Guam, the Northern Mariana Islands, and the United States Minor Outlying Islands.

The United States has a federal structure, with its 50 states enjoying a high degree of autonomy and self-government. The United States has the largest economy in the world, controlled almost completely by the private sector.

America has for centuries been a country of high immigration, and the population includes a large number of different races and nationalities from around the world, many attracted by the freedom and opportunities offered by the United States. American culture has spread around the world through the influence of TV and cinema, contributing to a continuing inflow of foreign nationals chasing “The American Dream.”

While earlier European immigrants who came to America in the 19th and early 20th centuries tended to assimilate into the existing population, recent groups such as the many Hispanic groups have kept their own cultural and ethnic identities to a greater extent. There are major differences between regions of the United States in the racial and ethnic composition of their local populations, with the highest concentrations of recent immigrants, mainly from Mexico and other Latin America countries, living in California and the New York City area.

For more information regarding the demographic make-up of the US, visit the US Census Bureau's web site at www.census.gov.

Although rates of immigration to the United States from other western countries are relatively low these days, all of America's main cities and many of its towns have very cosmopolitan populations with foreign nationals from all over the world, some of whom are working in the United States on a temporary basis, others who are there permanently and seeking to become citizens. In some parts of rural America, however, the population is predominantly white, while other areas such as the southern states have particularly large African-Caribbean populations.

The Immigration Statistics Yearbook published by the State Department (www.dhs.gov/ximgtn/statistics/publications/yearbook.shtm) and the Immigration Statistics published by the Department of Homeland Security (www.dhs.gov/ximgtn/statistics) has more information about immigration rates.