At the beginning of the 1960s, Americans could be forgiven for thinking that they were standing at the dawn of a golden age. Superficially, at least, the years since the end of World War II had been marked by progress, prosperity, moderation and old-fashioned good sense, and there was no reason to think that the 60s would be any different. But, of course, they were. The 50s had hula hoops; the 60s had acid tests. The 50s had Levittown; the 60s had Watts. The 50s had cars with fins; the 60s had tanks and Napalm bombs. The discontent that had percolated under the surface of the placid 50s defined the tumultuous 60s, along with a rising tide of rights-consciousness. African-Americans, young people, women, gays and lesbians, American Indians, Hispanics and others began to demand - not for the first time, but more loudly than ever - that they be permitted to participate fully and equally in the social, economic, and political life of the United States. Their challenges shook the nation to its core.

Most of all, this was a decade for young people. It was no wonder: For one thing, there were more of them than ever before. In 1960, nearly half of Americans were younger than 18, and in 1970 more than half were younger than 30. These men and women spent the decade in high school and college, at war and on communes, trying to make sense of the world around them. They also had plenty of disposable income, and the things that they bought - the culture they created - reflected their new values and concerns.

By the end of the 60s, it seemed that the nation would be consumed by rebellion - but at the beginning of the decade, the years ahead seemed full of promise. On January 20, 1961, the handsome and charismatic John F. Kennedy became president of the United States. In his campaign, he had promised an ambitious program of domestic legislation called the New Frontier, and now that he had eked out a victory over the much less vigorous and telegenic Vice-President Nixon he was ready to get started. For the first time since the New Deal, the federal government was willing and able to tackle issues like poverty, inequality and injustice that many people in the 50s had been happy to ignore. It turned out that most of the New Frontier was a non-starter, since Kennedy did not have much of a mandate and the Democrats' Congressional majority depended on a group of conservative southerners who thought the federal government should keep to itself. Still, the idea of the New Frontier - the sense that "the government possessed big answers to big problems," as one historian put it - was an incredibly powerful one.

This idea survived even after JFK was assassinated in November 1963. The new president, Lyndon B. Johnson, was as committed to the active use of presidential power as his predecessor had been - and now he had the political capital to enact an expansive program of reforms. In 1964 he declared that he would make the United States into a "Great Society" in which poverty and racial injustice had no place. He developed a set of programs that would give poor people "a hand up, not a hand out." These included Medicare and Medicaid, which helped elderly and poor people pay for health care; Head Start, which prepared young children for school; and a Job Corps that trained unskilled workers for jobs in the de-industrializing economy. Meanwhile, Johnson's Office of Economic Opportunity encouraged poor people themselves to participate in the design and implementation of the government's programs on their behalf, while his Model Cities program offered federal subsidies for urban redevelopment and community projects.

Unfortunately, the War on Poverty ran headlong into the war in Vietnam, and there simply wasn't enough money for both. Conflict in Vietnam had been going on since the 1950s, and the United States had intervened cautiously, wanting to prevent the spread of communism without getting too involved. But by the time President Johnson took office, it was too late - he had inherited a substantial American commitment to anti-communist South Vietnam. Soon he escalated that commitment into a full-scale war. In 1964, after the president claimed that Vietnamese torpedoes had struck American destroyers in the Gulf of Tonkin (not quite true, it later turned out), Congress authorized the president to take "all necessary measures" to protect American soldiers and their allies from the communist Viet Cong. Within days, the draft began. The war dragged on, growing bloodier, more expensive and more pointless each year. And it divided the nation. Some young people took to the streets in protest, while others fled to Canada to avoid the draft. Meanwhile, many of their parents and many of their peers formed a "silent majority" in support of the government's policies.

At the same time, the limits of the Great Society were becoming obvious. The struggle for civil rights had defined the 60s ever since four black students sat down at a whites-only lunch counter in Greensboro, North Carolina, in February 1960 and refused to leave. Their movement spread: Hundreds of demonstrators went back to that lunch counter every day, and tens of thousands clogged segregated restaurants and shops across the upper South. The protesters drew the nation's attention to the galling injustices - as well as the brutality and capriciousness - that characterized Jim Crow.

There were a few exceptions - marshals accompanied black Air Force vet James Meredith to his first day at the all-white University of Mississippi, for example - but in general, the federal government stayed out of the civil rights struggle until 1964, when President Johnson finally pushed a Civil Rights Act through Congress. The act prohibited discrimination in public places, gave the Justice Department permission to sue states that discriminated against women and minorities, and promised equal opportunities in the workplace to all. The next year, the Voting Rights Act eliminated poll taxes, literacy requirements and other tools that southern whites had traditionally used to keep blacks from voting.

But some people doubted that all this reform was enough. Clearly, African-Americans were still plagued by poverty, injustice and simple racism. Many black leaders began to think twice about their goals. Maybe separatism would be more effective than integration after all; maybe self-defense would be more powerful than non-violent resistance.

And just as black power became the new focus of the civil rights movement in the mid-1960s, other groups were growing similarly impatient with incremental reforms. Student activists grew more radical. They took over college campuses, organized massive anti-war demonstrations and occupied parks and other public places. Some even made bombs and set campus buildings on fire. Young women who had read The Feminine Mystique, celebrated the passage of the 1963 Equal Pay Act and joined the moderate National Organization for Women were also increasingly annoyed with the slow progress of reform. Many felt that their male counterparts in the civil rights movement, the student movement, and the counterculture - young men who professed a commitment to egalitarianism and community - exploited and abused them. They, too, grew more militant.

Likewise, the counterculture seemed to grow more outlandish as the decade wore on. Some young people had "dropped out" of political life altogether. They grew their hair long and wore loud clothes, smoked pot and dropped acid, and - thanks to the newly-accessible birth-control pill - had a lot of sex. They scorned traditional middle-class decorum and used foul language. Some moved to communes. Most of all, they listened to new kinds of music. Early in the decade, folk singers like Bob Dylan, Joan Baez and Peter, Paul and Mary revived idealistic anthems of the 1930s and wrote optimistic songs that celebrated democracy and community. Meanwhile, soul singers from record labels like Detroit's Motown and Memphis' Stax sang songs about oppression and empowerment. Later on, rock bands like Jefferson Airplane, the Rolling Stones and the Grateful Dead reflected young people's growing disillusionment with liberalism. Some advocated revolution; others simply turned inward, away from politics.

The optimistic 60s went sour for good in 1968. That year, the tenuous Cold War consensus on Vietnam shattered once and for all when the North Vietnamese Tet Offensive proved that, indeed, the war would be impossible to win. The Democratic Party split: At the end of March, LBJ went on TV to announce that he was ending his reelection campaign. (Richard Nixon, chief spokesman for the silent majority, won the election that fall.) Martin Luther King Jr. and Bobby Kennedy, the two most visible leftists in American politics, were assassinated. Police used tear gas and billy clubs to break up protests at the Democratic National Convention in Chicago. Furious anti-war protestors took over Columbia University in New York as well as the Sorbonne in Paris and the Free University in Berlin. And the urban riots that had erupted across the country every summer since 1964 continued and intensified.

Shreds of the hopeful 60s remained - in the summer of 1969, for example, more than 400,000 young people trooped to the Woodstock music festival in upstate New York, a harmonious three days that seemed to represent the best of the peace-and-love generation. By the end of the decade, however, community and consensus lay in tatters. The era's legacy is mixed - it brought us empowerment and polarization, resentment and liberation - but it was clear that it became a permanent part of our political and cultural lives.