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 forty-eight 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, scattered around the Caribbean and Pacific.
Washington, D.C. (formally, the District of Columbia and commonly referred to as Washington, the District, or simply D.C.) is the capital of the United States, founded on July 16, 1790. The City of Washington was originally a separate municipality within the Territory of Columbia until an Act of Congress in 1871 effectively merged the City and the Territory into a single entity called the District of Columbia. It is for this reason that the city, while legally named the District of Columbia, is known as Washington, D.C. The city is located on the north bank of the Potomac River and is bordered by the states of Virginia to the southwest and Maryland to the other sides. The District has a resident population of 588,292; however, due to commuters from the surrounding suburbs, its population rises to over one million during the workweek. The Washington Metropolitan Area, of which the District is a part, has a population of 5.3 million, the eighth-largest metropolitan area in the country.
San Diego is a large coastal city in Southern California, which is located in the southwestern corner of the continental United States. The state of California put the city's population at 1,336,865. It is the second largest city in California and the eighth largest city in the United States, by population. It is the county seat of San Diego County and is the economic center of the San Diego-Carlsbad-San Marcos metropolitan area, the 17th-largest in the United States with a population of 3,146,274 as of 2008, and the 21st-largest metropolitan area in the Americas when including Tijuana.
