Table of Contents
United States of America - 20th Century History
The 20th century was the period in which the United States rose from a regional industrial power to the dominant military, economic, and cultural force in the world. Beginning in 1900 and ending with the dissolution of the Soviet Union's legacy order in the 1990s, the century encompassed two world wars, the Great Depression, the extended Cold War rivalry with the USSR, the dismantling of legal racial segregation, and repeated cycles of political realignment. The United States entered the century as a nation still consolidating its continental territory and its overseas acquisitions from the Spanish-American War; it ended the century as the world's sole superpower, its economy the largest in history.
For a more detailed narrative treatment, see United States of America - History.
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Progressive Era (1900–1920)
The first two decades of the century were defined by the Progressive Era, a broad reform movement responding to the social and economic dislocations of industrial capitalism. Major constitutional changes included the Sixteenth Amendment (1913), authorizing a federal income tax; the Seventeenth Amendment (1913), establishing direct election of U.S. senators; and the Nineteenth Amendment (1920), extending the right to vote to women. Decades of organizing by the women's suffrage movement preceded that final legislative achievement. Federal regulatory capacity expanded significantly, with new agencies and legislation targeting monopolies, food and drug safety, banking, and working conditions.
Woodrow Wilson, president from 1913 to 1921, presided over much of this legislative activity and led the country into World War I in April 1917. The United States' entry accelerated the Allied victory; the armistice took effect in November 1918. Wilson's attempt to commit the country to the League of Nations at the war's conclusion was defeated in the Senate, a rejection that remains a contested episode in the history of American internationalism; see United States of America - Foreign Policy: History.
The 1920s and Prohibition
The decade following World War I brought economic expansion, rapid cultural change, and the national experiment of Prohibition (1920–1933), enacted through the Eighteenth Amendment. The decade was marked by mass consumerism, the growth of the automobile industry, the expansion of radio, and significant immigration before the restrictive Immigration Act of 1924 sharply curtailed arrivals from Southern and Eastern Europe. The first wave of the Great Migration — the movement of millions of Black Americans from the rural South to Northern and Midwestern cities, which had begun around 1910 — continued through the decade, reshaping the demographics of American cities and the composition of the New Deal political coalition that followed. The Harlem Renaissance produced a substantial body of Black artistic and intellectual work centered in New York City. The decade ended abruptly with the stock market crash of October 1929.
The Great Depression and the New Deal (1929–1939)
The Great Depression, initiated by the 1929 crash and deepened by banking collapses and contractionary monetary policy, was the most severe economic crisis in American history. Unemployment reached approximately 25 percent at its peak. Franklin D. Roosevelt, elected in 1932, responded with the New Deal — a sweeping program of banking stabilization, emergency relief, public works, agricultural adjustment, and financial regulation that fundamentally enlarged the federal government's role in the economy. Whether the New Deal restored prosperity, prolonged the depression, or set necessary institutional precedents is a subject of substantial ongoing debate; see United States of America - New Deal: Viewpoints.
World War II (1941–1945)
The Japanese attack on Pearl Harbor on December 7, 1941 brought the United States into World War II. American forces fought in both the Pacific and European theaters. Industrial mobilization transformed the economy and drew millions of women and minorities into the workforce. A second major wave of the Great Migration accelerated during the war years, as defense industry employment drew Black workers to Northern and Western cities in large numbers. The war in Europe ended with German surrender in May 1945. The war in the Pacific ended in August 1945, following the atomic bombings of Hiroshima and Nagasaki — a decision whose ethics and military necessity continue to be actively debated; see United States of America - Atomic Bombings: Viewpoints. The wartime internment of Japanese Americans under Executive Order 9066 has also been the subject of persistent legal and historical controversy.
The United States emerged from the war as one of two global superpowers, possessing nuclear weapons and an undamaged industrial base while most other major belligerents faced extensive reconstruction.
The Cold War (1947–1991)
The Cold War — the extended geopolitical and ideological contest between the United States and the Soviet Union — shaped American foreign and domestic policy across four decades. The containment doctrine, articulated by diplomat George Kennan and adopted as official policy, held that Soviet expansionism should be checked at each point of advance rather than rolled back by force.
American military engagement under this framework included the Korean War (1950–1953), which ended in a 1953 armistice along roughly the prewar boundary, with no formal peace treaty concluded. The Vietnam War (roughly 1955–1975) escalated from an advisory mission under Dwight Eisenhower and John F. Kennedy to a major ground war under Lyndon B. Johnson, eventually involving over 500,000 American troops at its peak. The war ended with American withdrawal and the fall of South Vietnam in 1975. The war's origins, conduct, and legacy remain subjects of significant historical and political disagreement; see United States of America - Vietnam War: Viewpoints.
The Cuban Missile Crisis of October 1962, in which the United States and Soviet Union came to the edge of nuclear conflict over the placement of Soviet missiles in Cuba, was resolved through negotiated withdrawal. McCarthyism — the investigation and accusation of alleged communist influence in American institutions, associated with Senator Joseph McCarthy — peaked in the early 1950s and subsided following televised hearings in 1954. Its scope, legitimacy, and long-term effects are treated in United States of America - McCarthyism: Viewpoints.
The Cold War produced a permanent national security apparatus, a massive nuclear arsenal, a global network of military alliances centered on NATO, and extensive covert operations across the developing world. It formally ended with the dissolution of the Soviet Union in December 1991.
The Civil Rights Movement
The Civil Rights Movement of the 1950s and 1960s dismantled the legal structure of Jim Crow racial segregation through litigation, nonviolent direct action, and federal legislation. //Brown v. Board of Education// (1954) overturned the separate-but-equal doctrine established in //Plessy v. Ferguson// (1896). The Montgomery Bus Boycott (1955–1956) brought Martin Luther King Jr. to national prominence. The Civil Rights Act of 1964 and the Voting Rights Act of 1965 prohibited racial discrimination in public accommodations and employment and protected Black voting rights, respectively.
The movement's internal debates over strategy, leadership, and goals — including the divergent approaches of King's Southern Christian Leadership Conference, the Student Nonviolent Coordinating Committee, and the Black Power movement — are treated in United States of America - Civil Rights Movement History.
The 1960s
The 1960s were a decade of compressed political crisis. President John F. Kennedy was assassinated in Dallas in November 1963; Martin Luther King Jr. and Robert Kennedy were both assassinated in 1968. The escalation of Vietnam produced large-scale antiwar protests and a deep fracture in public trust in the government. Urban unrest following King's assassination and throughout the decade resulted in widespread riots in major American cities. The counterculture challenged prevailing norms around sexuality, drug use, military service, and institutional authority. Lyndon B. Johnson's Great Society programs significantly expanded the federal welfare state, including the creation of Medicare and Medicaid in 1965.
Nixon, Watergate, and the 1970s
Richard Nixon's presidency (1969–1974) achieved the opening of diplomatic relations with China, negotiated the withdrawal from Vietnam under the Paris Peace Accords (1973), and established the Environmental Protection Agency. It ended in Nixon's resignation in August 1974 following the Watergate scandal — a political burglary and subsequent cover-up that produced constitutional proceedings and two years of congressional investigation. Nixon remains the only U.S. president to have resigned from office.
The 1970s were characterized by stagflation — the simultaneous occurrence of high inflation and high unemployment, which challenged prevailing Keynesian economic assumptions — and by the energy crises of 1973 and 1979, precipitated by OPEC oil embargoes. The decade also saw the //Roe v. Wade// decision (1973), in which the Supreme Court recognized a constitutional right to abortion; the ruling was the subject of sustained political and legal conflict for the following five decades.
The Reagan Era and the End of the Cold War
Ronald Reagan's election in 1980 represented a significant political realignment. Reagan's domestic program — tax cuts, deregulation, reductions in domestic spending, and a more confrontational posture toward organized labor — reflected a break with the New Deal governance consensus that had prevailed since the 1930s. Supply-side economics — the theory that reducing marginal tax rates and regulation stimulates broad economic growth — was the framework; its effects are disputed; see United States of America - Reaganomics: Viewpoints.
Reagan's Cold War posture combined a significant military buildup with direct and covert support for anti-communist movements, including the Iran-Contra affair — a covert scheme to fund Nicaraguan rebels using proceeds from arms sales to Iran — which produced significant scandal. The Soviet Union, under Mikhail Gorbachev, undertook internal reform that accelerated its collapse; the Soviet Union dissolved in December 1991, during the presidency of George H.W. Bush.
The 1990s
The decade following the Cold War brought American economic expansion driven in part by the growth of the internet economy. Bill Clinton's two-term presidency (1993–2001) pursued centrist economic policies including NAFTA (1994), welfare reform, and fiscal balance, while also seeing the impeachment of Clinton in 1998 on charges of perjury and obstruction of justice arising from a civil lawsuit and independent counsel investigation. Clinton was acquitted by the Senate.
The decade also produced the Oklahoma City bombing (1995), the deadliest domestic terrorist attack in American history to that point, carried out by anti-government extremists. American military engagements of the decade included the Gulf War (1990–1991), the intervention in Somalia, and NATO operations in the former Yugoslavia.
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See Also
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