History of the United States in the context of "Parallel 36°30′ north"

The United States Armed Forces are the military forces of the United States. U.S. federal law names six armed forces: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. Since 1949, all of the armed forces, except the Coast Guard, have been permanently part of the United States Department of Defense, with the Space Force existing as a branch of the Air Force until 2019. They form six of the eight uniformed services of the United States.

From their inception during the American Revolutionary War, the Army and the Navy, and later the other services, have played a decisive role in the country's history. They helped forge a sense of national unity and identity through victories in the early-19th-century First and Second Barbary Wars. They played a critical role in the territorial evolution of the U.S., including the American Civil War. The National Security Act of 1947 created the Department of Defense or DoD, (after a short period being called the National Military Establishment) headed by the secretary of defense, superior to the service secretaries. It also created both the U.S. Air Force and National Security Council; in 1949, an amendment to the act merged the cabinet-level departments of the Army, Navy, and Air Force into the DoD.

Immigration has been a major source of population growth and cultural change in the United States throughout much of its history. As of January 2025, the United States has the largest immigrant population in the world in absolute terms, with 53.3 million foreign-born residents, representing 15.8% of the total U.S. population—both record highs. While the United States represented about 4% of the total global population in 2024, 17% of all international migrants resided in the United States. In March 2025, the Federation for American Immigration Reform (FAIR) estimated that approximately 18.6 million illegal immigrants resided in the United States. In 2024, immigrants and their U.S.-born children number more than 93 million people, or 28% of the total U.S. population.According to the 2016 Yearbook of Immigration Statistics, the United States admitted a total of 1.18 million legal immigrants (618k new arrivals, 565k status adjustments) in 2016. Of these, 48% were the immediate relatives of United States citizens, 20% were family-sponsored, 13% were refugees or asylum seekers, 12% were employment-based preferences, 4.2% were part of the Diversity Immigrant Visa program, 1.4% were victims of a crime (U1) or their family members were (U2 to U5), and 1.0% who were granted the Special Immigrant Visa (SIV) for Iraqis and Afghans employed by the United States Government. The remaining 0.4% included small numbers from several other categories, including 0.2% who were granted suspension of deportation as an immediate relative of a citizen (Z13); persons admitted under the Nicaraguan and Central American Relief Act; children born after the issuance of a parent's visa; and certain parolees from the former Soviet Union, Cambodia, Laos, and Vietnam who were denied refugee status.

Between 1921 and 1965 policies such as the National Origins Formula limited immigration and naturalization opportunities for people from areas outside Northwestern Europe. Exclusion laws enacted as early as the 1880s generally prohibited or severely restricted immigration from Asia, and quota laws enacted in the 1920s curtailed Southern and Eastern European immigration. The civil rights movement led to the replacement of these ethnic quotas with per-country limits for family-sponsored and employment-based preference visas. Between 1970 and 2007, the number of first-generation immigrants living in the United States quadrupled from 9.6 million to 38.1 million residents. Census estimates show 45.3 million foreign born residents in the United States as of March 2018 and 45.4 million in September 2021, the lowest three-year increase in decades.

The Reconstruction era was a period in US history that followed the American Civil War (1861–1865) and was dominated by the legal, social, and political challenges of the abolition of slavery and reintegration of the former Confederate States into the United States. Three amendments were added to the United States Constitution to grant citizenship and equal civil rights to the newly freed slaves. To circumvent these, former Confederate states imposed poll taxes and literacy tests and engaged in terrorism to intimidate and control African Americans and discourage or prevent them from voting.

Throughout the war, the Union was confronted with the issue of how to administer captured areas and handle slaves escaping to Union lines. The United States Army played a vital role in establishing a free labor economy in the South, protecting freedmen's rights, and creating educational and religious institutions. Despite its reluctance to interfere with slavery, Congress passed the Confiscation Acts to seize Confederates' slaves, providing a precedent for President Abraham Lincoln to issue the Emancipation Proclamation. Congress established a Freedmen's Bureau to provide much-needed food and shelter to the newly freed slaves. As it became clear the Union would win, Congress debated the process for readmission of seceded states. Radical and moderate Republicans disagreed over the nature of secession, conditions for readmission, and desirability of social reforms. Lincoln favored the "ten percent plan" and vetoed the Wade–Davis Bill, which proposed strict conditions for readmission. Lincoln was assassinated in 1865, just as fighting was drawing to a close. He was replaced by Andrew Johnson, who vetoed Radical Republican bills, pardoned Confederate leaders, and allowed Southern states to enact draconian Black Codes that restricted the rights of freedmen. His actions outraged many Northerners and stoked fears the Southern elite would regain power. Radical Republicans swept to power in the 1866 midterm elections, gaining majorities in both houses of Congress.

Throughout U.S. history, the country experienced successive waves of immigration, particularly from Europe and later on from Asia and from Latin America. Colonial-era immigrants often repaid the cost of transoceanic transportation by becoming indentured servants where the employer paid the ship's captain. In the late 19th century, immigration from China and Japan was restricted. In the 1920s, restrictive immigration quotas were imposed but political refugees had special status. Numerical restrictions ended in 1965. In recent years, the largest numbers of immigrants to the United States have come from Asia and Central America (see Central American crisis).

Attitudes towards new immigrants have fluctuated from favorable to hostile since the 1790s. Recent debates have focused on the southern border (see Illegal immigration to the United States and Mexico–United States border wall) and the status of "dreamers", people who illegally migrated with their families when they were children and have lived in the U.S. for almost their entire lives (see Deferred Action for Childhood Arrivals).

The Constitutional Convention took place in Philadelphia from May 25 to September 17, 1787. While the convention was initially intended to revise the league of states and the first system of federal government under the Articles of Confederation, leading proponents of the Constitutional Convention, including James Madison of Virginia and Alexander Hamilton of New York, sought to create a new frame of government rather than revise the existing one. Delegates elected George Washington of Virginia, former commanding general of the Continental Army in the American Revolutionary War and a proponent of a stronger national government, to serve as president of the convention. While the Constitutional Convention has been the only Federal one, the fifty states have held 233 constitutional conventions. The convention ultimately debated and ratified the Constitution of the United States, making the convention one of the most significant events in American history.

The convention took place in Pennsylvania State House, later renamed Independence Hall, in Philadelphia. The convention was not referred to as a constitutional convention. It was contemporarily known as the Federal Convention, the Philadelphia Convention, or the Grand Convention at Philadelphia. Most delegates did not arrive intending to draft a new constitution. Many assumed that the convention's purpose was to discuss and draft improvements to the existing Articles of Confederation, and would not have agreed to participate otherwise. Once the convention began, however, most of the delegates – though not all – came to agree in general terms that the goal would be a new system of government, not simply a revised version of the Articles of Confederation.

The values and ideals of republicanism are foundational in the constitution and history of the United States. As the United States constitution prohibits granting titles of nobility, republicanism in this context does not refer to a political movement to abolish such a social class, as it does in countries such as the United Kingdom, Australia, and the Netherlands. Instead, it refers to the core values that citizenry in a republic have, or ought to have.

Political scientists and historians have described these central values as liberty and inalienable individual rights; recognizing the sovereignty of the people as the source of all authority in law; rejecting monarchy, aristocracy, and hereditary political power; virtue and faithfulness in the performance of civic duties; and vilification of corruption. These values are based on those of Ancient Greco-Roman, Renaissance, and English models and ideas. Articulated in the writings of the Founding Fathers (particularly Thomas Jefferson, James Madison, and John Adams), they formed the intellectual basis for the American Revolution – the Declaration of Independence (1776), the Constitution (1787), and the Bill of Rights (1791), as well as the Gettysburg Address (1863).

The culture of the United States encompasses various social behaviors, institutions, and norms, including forms of speech, literature, music, visual arts, performing arts, food, sports, religion, law, technology, as well as other customs, beliefs, and forms of knowledge. American culture has been shaped by the history of the United States, its geography, and various internal and external forces and migrations.

America's foundations were initially Western-based, and primarily English-influenced, but also with prominent French, German, Greek, Irish, Italian, Scottish, Welsh, Jewish, Polish, Scandinavian, Spanish and Portuguese regional influences. However, non-Western influences, including African and Indigenous cultures, and more recently, Asian cultures, have firmly established themselves in the fabric of American culture as well. Since the United States was established in 1776, its culture has been influenced by successive waves of immigrants, and the resulting "melting pot" of cultures has been a distinguishing feature of its society. Americans pioneered or made great strides in musical genres such as heavy metal, rhythm and blues, jazz, gospel, country, hip hop, and rock 'n' roll. The "big four sports" are American football, baseball, basketball, and ice hockey. In terms of religion, the majority of Americans are Protestant or Catholic, with a growing irreligious population. American cuisine includes popular tastes such as hot dogs, milkshakes, and barbecue, as well as many other class and regional preferences. The most commonly used language is English; while no law designates it official, a 2025 executive order declares English the official language. Distinct cultural regions include New England, Mid-Atlantic, the South, Midwest, Southwest, Mountain West, and Pacific Northwest.

The Great Migration, sometimes known as the Great Northward Migration or the Black Migration, was the movement of five million African Americans out of the rural Southern United States to the urban Northeast, Midwest, and West between 1910 and 1970. It was substantially caused by poor economic and social conditions due to prevalent racial segregation and discrimination in the Southern states where Jim Crow laws were upheld. In particular, continued lynchings motivated a portion of the migrants, as African Americans searched for social reprieve. The historic change brought by the migration was amplified because the migrants, for the most part, moved to the then-largest cities in the United States (New York City, Chicago, Los Angeles, San Francisco, Philadelphia, Detroit, Cleveland, and Washington, D.C.) at a time when those cities had a central cultural, social, political, and economic influence over the United States; there, African Americans established culturally influential communities of their own. According to Isabel Wilkerson, despite the losses they felt leaving their homes in the South, and despite the barriers that the migrants faced in their new homes, the migration was an act of individual and collective agency, which changed the course of American history, a "declaration of independence" that was written by their actions.

From the earliest U.S. population statistics in 1780 until 1910, more than 90% of the African-American population lived in the American South, making up the majority of the population in three Southern states, namely Louisiana (until about 1890), South Carolina (until the 1920s), and Mississippi (until the 1930s). But by the end of the Great Migration, just over half of the African-American population lived in the South, while a little less than half lived in the North and West. Moreover, the African-American population had become highly urbanized. In 1900, only one-fifth of African Americans in the South were living in urban areas. By 1960, half of the African Americans in the South lived in urban areas, and by 1970, more than 80% of African Americans nationwide lived in cities. In 1991, Nicholas Lemann wrote: