Native Americans and European settlers

The indigenous peoples of the U.S. mainland, including Alaska Natives, migrated from Asia. They began arriving at least 12,000 and as many as 40,000 years ago. Some, such as the pre-Columbian Mississippian culture, developed advanced agriculture, grand architecture, and state-level societies. In 1492, Genoese explorer Christopher Columbus, under contract to the Spanish crown, reached several Caribbean islands, making first contact with the indigenous people. Millions of indigenous Americans subsequently died from epidemics of Eurasian diseases.
The Mayflower transported Pilgrims to the New World in 1620, as depicted in William Halsall's The Mayflower in Plymouth Harbor, 1882

On April 2, 1513, Spanish conquistador Juan Ponce de León landed on what he called "La Florida"—the first documented European arrival on what would become the U.S. mainland. Of Spain's settlements in the region, only St. Augustine, founded in 1565, remains. Later Spanish settlements in the present-day southwestern United States drew thousands through Mexico. French fur traders established outposts of New France around the Great Lakes; France eventually claimed much of the North American interior, down to the Gulf of Mexico. The first successful English settlements were the Virginia Colony in Jamestown in 1607 and the Pilgrims' Plymouth Colony in 1620. The 1628 chartering of the Massachusetts Bay Colony resulted in a wave of migration; by 1634, New England had been settled by some 10,000 Puritans. Between the late 1610s and the American Revolution, about 50,000 convicts were shipped to Britain's American colonies. Beginning in 1614, the Dutch settled along the lower Hudson River, including New Amsterdam on Manhattan Island.

In 1674, the Dutch ceded their American territory to England; the province of New Netherland was renamed New York. Many new immigrants, especially to the South, were indentured servants—some two-thirds of all Virginia immigrants between 1630 and 1680. By the turn of the century, African slaves were becoming the primary source of bonded labor. With the 1729 division of the Carolinas and the 1732 colonization of Georgia, the thirteen British colonies that would become the United States of America were established. All had local governments with elections open to most free men, with a growing devotion to the ancient rights of Englishmen and a sense of self-government stimulating support for republicanism. All legalized the African slave trade. With high birth rates, low death rates, and steady immigration, the colonial population grew rapidly. The Christian revivalist movement of the 1730s and 1740s known as the Great Awakening fueled interest in both religion and religious liberty. In the French and Indian War, British forces seized Canada from the French, but the francophone population remained politically isolated from the southern colonies. Excluding the Native Americans (popularly known as "American Indians"), who were being displaced, those thirteen colonies had a population of 2.6 million in 1770, about one-third that of Britain; nearly one in five Americans were black slaves. Though subject to British taxation, the American colonials had no representation in the Parliament of Great Britain.

Independence and expansion
American Revolution, American Revolutionary War, and Manifest Destiny
Declaration of Independence, by John Trumbull, 1817–18
Tensions between American colonials and the British during the revolutionary period of the 1760s and early 1770s led to the American Revolutionary War, fought from 1775 through 1781. On June 14, 1775, the Continental Congress, convening in Philadelphia, established a Continental Army under the command of George Washington. Proclaiming that "all men are created equal" and endowed with "certain unalienable Rights," the Congress adopted the Declaration of Independence, drafted largely by Thomas Jefferson, on July 4, 1776. That date is now celebrated annually as America's Independence Day. In 1777, the Articles of Confederation established a weak federal government that operated until 1789.

After the British defeat by American forces who were assisted by the French, Great Britain recognized the independence of the United States and the states' sovereignty over American territory west to the Mississippi River. A constitutional convention was organized in 1787 by those wishing to establish a strong national government, with powers of taxation. The United States Constitution was ratified in 1788, and the new republic's first Senate, House of Representatives, and president—George Washington—took office in 1789. The Bill of Rights, forbidding federal restriction of personal freedoms and guaranteeing a range of legal protections, was adopted in 1791.

Attitudes toward slavery were shifting; a clause in the Constitution protected the African slave trade only until 1808. The Northern states abolished slavery between 1780 and 1804, leaving the slave states of the South as defenders of the "peculiar institution." The Second Great Awakening, beginning about 1800, made evangelicalism a force behind various social reform movements, including abolitionism.
Territorial acquisitions by date

Americans' eagerness to expand westward prompted a long series of Indian Wars and an Indian removal policy that stripped the native peoples of their land. The Louisiana Purchase of French-claimed territory under President Thomas Jefferson in 1803 almost doubled the nation's size. The War of 1812, declared against Britain over various grievances and fought to a draw, strengthened U.S. nationalism. A series of U.S. military incursions into Florida led Spain to cede it and other Gulf Coast territory in 1819. The U.S. annexed the Republic of Texas in 1845. The concept of Manifest Destiny was popularized during this time.[31] The 1846 Oregon Treaty with Britain led to U.S. control of the present-day American Northwest. The U.S. victory in the Mexican-American War resulted in the 1848 cession of California and much of the present-day American Southwest. The California Gold Rush of 1848–49 further spurred western migration. New railways made relocation easier for settlers and increased conflicts with Native Americans. Over a half-century, up to 40 million American bison, or buffalo, were slaughtered for skins and meat and to ease the railways' spread. The loss of the buffalo, a primary resource for the plains Indians, was an existential blow to many native cultures.