United States

The US is a federal republic comprising 50 states and the Federal District of Columbia. It originated in the American Revolution, the successful rebellion of the colonies on the eastern coast against British rule in 1775–83. The original 13 states that formed the Union drew up a federal constitution in 1787, and George Washington was elected the first president in 1789. In the 19th century the territory of the US was extended across the continent through the westward spread of pioneers and settlers and acquisitions such as that of Texas and California from Mexico in the 1840s. After a long period of isolation in foreign affairs, the US participated on the Allied side in both world wars and emerged from the Cold War as the world’s leading military and economic power