The United States of America (also called the United States, the U.S., the USA, America, and the States) 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 the 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 in the Pacific and Caribbean.
At 3.79 million square miles (9.83 million km) and with over 312 million people, the United States is the third or fourth largest country by total area, and the third largest by both land area and population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The U.S. economy is the world's largest national economy, with an estimated 2011 GDP of $15.1 trillion (22% of nominal global GDP and over 19% of global GDP
The United States dollar (sign: $; code: USD; also abbreviated US$), also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies.
The U.S. dollar is the currency most used in international transactions and is one of the world's reserve currencies. Several countries use it as their official currency and in many others it is the de facto currency,. It is also used as the sole currency in some British Overseas Territories (British Virgin Islands and Turks and Caicos).
The Constitution of the United States of America provides that the United States Congress shall have the power "To coin Money". Laws implementing this power are currently codified in Section 5112 of Title 31 of the United States Code. Section 5112 prescribes the forms in which the United States dollars shall be issued. Those coins are both designated in Section 5112 as "legal tender" in payment of debts. The Sacagawea dollar is one example of the copper alloy dollar. The pure silver dollar is known as the American Silver Eagle. Section 5112 also provides for the minting and issuance of other coins, which have values