America's involvement in the Vietnam War from 1964 to 1973 sparked significant domestic unrest during those years. Many young people protested the war, with demonstrations peaking in 1969 when 250,000 individuals marched in Washington, D.C. The following year, on May 4, 1970, National Guardsmen fatally shot four students at Kent State University in Ohio during a war protest. The mid to late 1960s also witnessed the emergence of the "counter-culture" in the United States. This movement grew largely in response to the war and consisted of young people who identified as "hippies" or "flower children." The counterculture aimed to create a society founded on love, happiness, peace, and freedom, rejecting materialism and traditional middle-class values. They protested against America's involvement in Vietnam, embraced spirituality, particularly Asian mysticism, advocated for a sexual revolution, and promoted the use of psychedelic drugs to expand consciousness. A popular slogan of the counterculture was "Make love, not war." In 1965, American poet Allen Ginsberg introduced the term "flower power" during an antiwar protest in Berkeley, California. This term described a strategy of peaceful resistance against perceived injustices. That same year, Harvard professor Timothy Leary published The Psychedelic Reader, where he shared his drug experiments and advised readers to "turn on, tune in, and drop out." In 1966, the International Society for Krishna Consciousness, founded in India in 1958, was brought to the United States and Canada. The Hare Krishnas rejected materialism and lived communally. In 1968, confrontations occurred between the counterculture and the political establishment at the Democratic National Convention in Chicago.

Members of the counterculture organized a "Festival of Life," where they protested the war, attended rock concerts, smoked marijuana, engaged in public sex, held beach "nude-ins," and burned draft cards. Rock 'n' roll was a vital part of the counterculture movement, and the first large rock gathering took place in Monterey, California, in 1967. In 1969, the Woodstock Music and Art Fair drew 300,000 attendees to a dairy farm in upstate New York.

During the 1960s, Lyndon Johnson, who assumed the presidency after John F. Kennedy's assassination in 1963, sought to build a "Great Society" through numerous laws advancing civil rights, aiding the poor, and protecting the environment. In 1965, the Appalachian Regional Development Act provided aid to the economically depressed region, and the Housing and Urban Development Act established a cabinet-level department to coordinate federal housing programs. The Medicare Act offered healthcare to the elderly, and the Higher Education Act provided scholarships for over 140,000 needy students. Additional legislation under Johnson's administration liberalized immigration laws, supported the arts, tackled truth in packaging issues, and addressed water and air quality.

This era in U.S. history is also notable for the civil rights movement. In March 1965, Dr. Martin Luther King Jr. led a march from Selma to Montgomery, Alabama, demanding federal protection for African Americans' voting rights. Later that year, the new Voting Rights Act was signed, eliminating literacy tests and other voting restrictions while authorizing federal intervention against voter discrimination. Additionally, in 1965, Thurgood Marshall became the first African American appointed to the U.S. Supreme Court. Tragically, in 1968, Dr. King was assassinated in Memphis, Tennessee.

The feminist movement also gained momentum during the late 1960s and early 1970s. The birth control pill was introduced in the United States in the mid-1960s, and in 1973, the Supreme Court's ruling in Roe vs. Wade declared that states could not prohibit a woman from having an abortion during the first trimester of pregnancy. The National Organization for Women (NOW) was established in 1966, led by Betty Friedan, who authored The Feminine Mystique in 1963. NOW's membership included many prominent women's rights activists, and the organization initially focused on combating discrimination against women in economic, educational, and social spheres. Numerous other women's groups emerged, including the National Women's Law Center in 1972, which aimed to protect women's rights, and the Women's Campaign Fund in 1973, which supported female political candidates.

Richard Nixon was reelected as president in 1972. However, it soon emerged that members of Nixon's Committee to Re-Elect the President had broken into the Democratic National Committee headquarters at the Watergate Hotel in June of that year. Nixon's efforts to conceal the scandal culminated in his resignation in August 1974, making him the only U.S. president to resign to avoid impeachment. The Watergate scandal, along with the Vietnam War, fostered growing disillusionment and skepticism towards American government and politics.

The period from 1965 to 1975 also witnessed significant scientific and technological advancements, particularly in space exploration. In 1965, the world's first commercial communications satellite was launched, and later that year, Edward White became the first American to walk in space. An unmanned American space probe landed on the moon in 1967, and in 1968, the first manned spacecraft orbited the moon. Neil Armstrong made history in 1969 by becoming the first person to set foot on the moon during the Apollo 11 mission.

1973: Numerous young individuals involved in the counterculture movement come together to establish communes, striving to coexist without the negative aspects of modern society. Many of these communities are founded in California and the Pacific Northwest.

1993: In Waco, Texas, several members of a religious commune known as the Branch Davidians lose their lives during a violent confrontation with U.S. federal agents.

1973: The United States records an infant mortality rate of 56 per 1,000 live births, ranking among the highest of all industrialized countries.

1994: The United States has an infant mortality rate of 31 per 1,000 live births, still among the highest of all Western industrialized nations and more than double Japan's rate.

1973: Following the Supreme Court's ruling on Roe v. Wade, which affirms a woman's right to privacy, abortion becomes legal throughout the United States.

1992: There are 1,359,000 abortions performed in the United States, equating to a ratio of 23 abortions for every 1,000 live births.