The first known inhabitants of modern-day United States territory are believed to have arrived over a period of several thousand years beginning sometime prior to 15,000 - 50,000 years ago by crossing Beringia into Alaska. Solid evidence of these cultures settling in what would become the US is dated to around 14,000 years ago.
Research has revealed much about the early Native American settlers of North America as indicated by Cyrus Thomas. Columbus' men were the first documented Old Worlders to land in the territory of what is now the United States when they arrived in Puerto Rico during their second voyage in 1493. Juan Ponce de León, who arrived in Florida in 1513, is credited as being the first European to land in what is now the continental United States, although some evidence suggests that John Cabot might have reached what is presently New England in 1498.
In its beginnings, the United States consisted only of the Thirteen Colonies, which consisted of states occupying the same lands as when they were British colonies. American colonists fought off the British army in the American Revolutionary War of the 1770s and issued a Declaration of Independence in 1776. Seven years later, the signing of the Treaty of Paris officially recognized independence from Britain. In the nineteenth century, westward expansion of United States territory began, upon the belief of Manifest Destiny, in which the United States would occupy all the North American land east to west, from the Atlantic to the Pacific Oceans. By 1912, with the admission of Arizona to the Union, the U.S. reached that goal. The outlying states of Alaska and Hawaii were both admitted in 1959.
Ratified in 1788, the Constitution serves as the supreme American law in organizing the government; the Supreme Court is responsible for upholding Constitutional law. Many social progresses came up starting in the nineteenth century; those advancements have been widely reflected in the Constitution. Slavery was...