The land which became the United States was inhabited by Native Americans for tens of thousands of years; their descendants include but may not be limited to 574 federally recognized tribes. The history of the present-day United States began in 1607 with the establishment of Jamestown in modern-day Virginia by settlers who arrived from the Kingdom of England, and the landing of the Mayflower by English pilgrims to Plymouth in 1620. In the late 15th century, European colonization began and largely decimated Indigenous societies through wars and epidemics. By the 1760s, the Thirteen Colonies, then part of British America and the Kingdom of Great Britain, were established. The Southern Colonies built an agricultural system on slave labor and enslaving millions from Africa. After the British victory over the Kingdom of France in the French and Indian Wars, Parliament imposed a series of taxes and issued the Intolerable Acts on the colonies in 1773, which were designed to end self-governance. Tensions between the colonies and British authorities subsequently intensified, leading to the Revolutionary War, which commenced with the Battles of Lexington and Concord on April 19, 1775. In June 1775, the Second Continental Congress established the Continental Army and unanimously selected George Washington as its commander-in-chief. The following year, on July 4, 1776, the Second Continental Congress unanimously declared its independence, issuing the Declaration of Independence. On September 3, 1783, in the Treaty of Paris, the British acknowledged the independence and sovereignty of the Thirteen Colonies, leading to the establishment of the United States. On September 17, 1787, the U.S. Constitution was signed by a majority of delegates, and was later ratified by the Thirteen Colonies, leading to the first modern U.S. government.
In the 1788-89 presidential election, Washington was elected the nation's first U.S. president. Along with his Treasury Secretary, Alexander Hamilton, Washington sought to create a relatively stronger central government than that favored by other founders, including Thomas Jefferson and James Madison. On March 4, 1789, the new nation debated, adopted, and ratified the U.S. Constitution, which is now the oldest and longest-standing written and codified national constitution in the world. In 1791, a Bill of Rights was added to guarantee inalienable rights. In 1803, Jefferson, then serving as the nation's third president, negotiated the Louisiana Purchase, which doubled the size of the country. Encouraged by available, inexpensive land, and the notion of manifest destiny, the country underwent westward expansion in a project of settler colonialism marked by a series of conflicts with the continent's indigenous inhabitants. The most notable advocate of manifest destiny was President James K. Polk, who annexed Texas in 1845, and declared war on Mexico the next year. An overwhelming U.S. victory in the Mexican-American War led to the Treaty of Guadalupe Hidalgo in 1848, where the U.S. acquired much of the American Southwest from Mexico. Whether or not slavery should be legal in the expanded territories was an issue of national contention, and led to increasing tensions over slavery.
