The US is a federal republic comprising fifty states and the Federal District of Columbia. It originated in the American War of Independence, the successful rebellion of the British colonies on the east coast in 1775-83. The original thirteen states which 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 (at the expense of the American Indian peoples), 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 came out of the Cold War as the world's leading military and economic power.