page_title: United States
section_title: Independence and expansion
hierarchical_section_title: United States / History / Independence and expansion
caption_attribution_description: English: San Francisco harbor (Yerba Buena Cove), 1850 or 1851, with Yerba Buena Island in the background. Daguerrotype. Română: Portul San Francisco (Golful Yerba Buena), la 1850 sau 1851; în fundal se vede Insula Yerba Buena. Dagherotip. Português do Brasil: Porto de San Francisco (Baía de Yerba Buena), em 1850 ou 1851, com a ilha de Yerba Buena Island ao fundo. Daguerrótipo.
context_page_description: The United States of America, commonly known as the United States or America, is a country mostly located in central North America, between Canada and Mexico. It consists of 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, it is the world's third- or fourth-largest country by total area. With a population of 328 million as of 2019, it is the third most populous country in the world. The capital is Washington, D.C., and the most populous city is New York City.
  Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago, and European colonization began in the 16th century. The United States emerged from the thirteen British colonies established along the East Coast. Disputes with Great Britain led to the American Revolutionary War, which established independence. In the late 18th century, the U.S. began vigorously expanding across North America, gradually acquiring new territories, oftentimes killing and displacing Native Americans, and admitting new states; by 1848, the United States spanned the continent.
context_section_description: The American Revolutionary War was the first successful colonial war of independence against a European power. Americans had developed an ideology of "republicanism", asserting that government rested on the will of the people as expressed in their local legislatures. They demanded their rights as Englishmen and "no taxation without representation". The British insisted on administering the empire through Parliament, and the conflict escalated into war.
  The Second Continental Congress unanimously adopted the Declaration of Independence. July 4—the declaration's anniversary—is celebrated annually as Independence Day. In 1777, the Articles of Confederation established a decentralized government that operated until 1789.
  After British defeat at the Battle of Yorktown in 1781, Britain signed a peace treaty. American sovereignty became internationally recognized and the country was granted all lands east of the Mississippi River. Tensions with Britain remained, however, leading to the War of 1812, which was fought to a draw. Nationalists led the Philadelphia Convention of 1787 in writing the United States Constitution, ratified in state conventions in 1788. The federal government was reorganized into three branches, on the principle of creating salutary checks and balances, in 1789. George Washington, who had led the Continental Army to victory, was the first president elected under the new constitution. The Bill of Rights, forbidding federal restriction of personal freedoms and guaranteeing a range of legal protections, was adopted in 1791.
  Although the federal government criminalized the international slave trade in 1808, after 1820, cultivation of the highly profitable cotton crop exploded in the Deep South, and along with it, the slave population. The Second Great Awakening, especially in the period 1800–1840, converted millions to evangelical Protestantism. In the North, it energized multiple social reform movements, including abolitionism; in the South, Methodists and Baptists proselytized among slave populations.
  Beginning in the late 18th century, Americans began to expand westward, prompting a long series of American Indian Wars. The 1803 Louisiana Purchase almost doubled the nation's area; Spain ceded Florida and other Gulf Coast territory in 1819; the Republic of Texas was annexed in 1845 during a period of expansionism; and the 1846 Oregon Treaty with Britain led to U.S. control of the present-day American Northwest. Victory in the Mexican–American War resulted in the 1848 Mexican Cession of California and much of the present-day American Southwest, making the U.S. span the continent.
  The California Gold Rush of 1848–49 spurred migration to the Pacific coast, which led to the California Genocide and the creation of additional western states. After the Civil War, new transcontinental railways made relocation easier for settlers, expanded internal trade and increased conflicts with Native Americans. In 1869, a new Peace Policy nominally promised to protect Native Americans from abuses, avoid further war, and secure their eventual U.S. citizenship. Nonetheless, large-scale conflicts continued throughout the West into the 1900s.
caption: San Francisco harbor during the California Gold Rush
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