The Stonewall riots were a series of spontaneous, violent demonstrations by members of the gay community against a police raid that took place in the early morning hours of June 28, 1969, at the Stonewall Inn in the Greenwich Village neighborhood of New York City. They are widely considered to constitute the single most important event leading to the gay liberation movement and the modern fight for LGBT rights in the United States.

Gay Americans in the 1950s and 1960s faced an anti-homosexual legal system. Early homophile groups in the U.S. sought to prove that gay people could be assimilated into society, and they favored non-confrontational education for homosexuals and heterosexuals alike. The last years of the 1960s, however, were very contentious, as many social movements were active, including the African American Civil Rights Movement, the Counterculture of the 1960s, and antiwar demonstrations. These influences, along with the liberal environment of Greenwich Village, served as catalysts for the Stonewall riots.

Very few establishments welcomed openly gay people in the 1950s and 1960s. Those that did were often bars, although bar owners and managers were rarely gay. At the time, the Stonewall Inn was owned by the Mafia. It catered to an assortment of patrons and was known to be popular among the poorest and most marginalized people in the gay community: drag queens, representatives of thetransgender community, effeminate young men, male prostitutes, and homeless youth. Police raids on gay bars were routine in the 1960s, but officers quickly lost control of the situation at the Stonewall Inn. They attracted a crowd that was incited to riot. Tensions between New York City police and gay residents of Greenwich Village erupted into more protests the next evening, and again several nights later. Within weeks, Village residents quickly organized into activist groups to concentrate efforts on establishing places for gays and lesbians to be open about their sexual orientation without fear of being arrested.

After the Stonewall riots, gays and lesbians in New York City faced gender, race, class, and generational obstacles to becoming a cohesive community. Within six months, two gay activist organizations were formed in New York, concentrating on confrontational tactics, and three newspapers were established to promote rights for gays and lesbians. Within a few years, gay rights organizations were founded across the U.S. and the world.

On June 28, 1970, the first Gay Pride marches took place in New York, Los Angeles, San Francisco and Chicago commemorating the anniversary of the riots. Similar marches were organized in other cities. Today, Gay Pride events are held annually throughout the world toward the end of June to mark the Stonewall riots.

The Stonewall Inn, located at 51 and 53 Christopher Street, along with several other establishments in the city, was owned by the Genovese family. In 1966, three members of the Mafia invested $3,500 to turn the Stonewall Inn into a gay bar, after it had been a restaurant and a nightclub for heterosexuals. Once a week a police officer would collect envelopes of cash as a payoff; the Stonewall Inn had no liquor license. It had no running water behind the bar—used glasses were run through tubs of water and immediately reused. There were no fire exits, and the toilets overran consistently. Though the bar was not used for prostitution, drug sales and other "cash transactions" took place. It was the only bar for gay men in New York City where dancing was allowed; dancing was its main draw since its re-opening as a gay club.

Visitors to the Stonewall Inn in 1969 were greeted by a bouncer who inspected them through a peephole in the door. The legal drinking age was 18, and to avoid unwittingly letting in undercover police (who were called "Lily Law," "Alice Blue Gown," or "Betty Badge"[46]), visitors would have to be known by the doorman, or look gay. The entrance fee on weekends was $3, for which the customer received two tickets that could be exchanged for two drinks. Patrons were required to sign their names in a book to prove that the bar was a private "bottle club," but rarely signed their real names. There were two dance floors in the Stonewall; the interior was painted black, making it very dark inside, with pulsing gel lights or black lights. If police were spotted, regular white lights were turned on, signaling that everyone should stop dancing or touching.

 In the rear of the bar was a smaller room frequented by "queens;" it was one of two bars where effeminate men who wore makeup and teased their hair (though dressed in men's clothing) could go. Only a few transvestites, or men in full drag, were allowed in by the bouncers. The customers were "98 percent male" but a few lesbians sometimes came to the bar. Younger homeless adolescent males, who slept in nearby Christopher Park, would often try to get in so customers would buy them drinks. The age clientele ranged between the upper teens and early thirties, and the racial mix was evenly distributed among white, black, and Hispanic patrons. Because of its even mix of people, its location, and the attraction of dancing, the Stonewall Inn was known by many as "the gay bar in the city."

Police raids on gay bars were frequent—occurring on average once a month for each bar. Many bars kept extra liquor in a secret panel behind the bar, or in a car down the block, to facilitate resuming business as quickly as possible if alcohol was seized. Bar management usually knew about raids beforehand due to police tip-offs, and raids occurred early enough in the evening that business could commence after the police had finished.

 During a typical raid, the lights were turned on, and customers were lined up and their identification cards checked. Those without identification or dressed in full drag were arrested; others were allowed to leave. Some of the men, including those in drag, used their draft cards as identification. Women were required to wear three pieces of feminine clothing, and would be arrested if found not wearing them. Employees and management of the bars were also typically arrested. The period immediately before June 28, 1969 was marked by frequent raids of local bars—including a raid at the Stonewall Inn on the Tuesday before the riots — and the closing of the Checkerboard, the Tele-Star, and two other clubs in Greenwich Village.

Christopher Street Liberation Day on June 28, 1970 marked the first anniversary of the Stonewall riots with an assembly on Christopher Street and the first Gay Pride march in U.S. history, covering the 51 blocks to Central Park. The march took less than half the scheduled time due to excitement, but also due to wariness about walking through the city with gay banners and signs. Although the parade permit was delivered only two hours before the start of the march, the marchers encountered little resistance from onlookers. The New York Times reported (on the front page) that the marchers took up the entire street for about 15 city blocks. Reporting by The Village Voice was positive, describing "the out-front resistance that grew out of the police raid on the Stonewall Inn one year ago."

There was little open animosity, and some bystanders applauded when a tall, pretty girl carrying a sign "I am a Lesbian" walked by. –The New York Times coverage of Gay Liberation Day, 1970.

Gay Pride marches took place simultaneously in Los Angeles and Chicago. The next year, Gay Pride marches took place in Boston, Dallas, Milwaukee,London, Paris, West Berlin, and Stockholm. By 1972 the participating cities included Atlanta, Buffalo, Detroit,Washington D.C., Miami, and Philadelphia, as well as San Francisco.

Frank Kameny soon realized the pivotal change brought by the Stonewall riots. An organizer of gay activism in the 1950s, he was used to persuasion, trying to convince heterosexuals that gay people were no different than they were. When he and other people marched in front of the White House, the State Department, and Independence Hall only five years earlier, their objective was to look as if they could work for the U.S. government. Ten people marched with Kameny then, and they alerted no press to their intentions. Although he was stunned by the upheaval by participants in the Annual Reminder in 1969, he later observed, "By the time of Stonewall, we had fifty to sixty gay groups in the country. A year later there was at least fifteen hundred. By two years later, to the extent that a count could be made, it was twenty-five hundred."

Similar to Kameny's regret at his own reaction to the shift in attitudes after the riots, Randy Wicker came to describe his embarrassment as "one of the greatest mistakes of his life." The image of gays retaliating against police, after so many years of allowing such treatment to go unchallenged, "stirred an unexpected spirit among many homosexuals."

Kay Lahusen, who photographed the marches in 1965, stated, "Up to 1969, this movement was generally called the homosexual or homophile movement... Many new activists consider the Stonewall uprising the birth of the gay liberation movement. Certainly it was the birth of gay pride on a massive scale." David Carter, in his article “What made Stonewall different,” explained that even though there were several uprisings before Stonewall, the reason Stonewall was so historical was that thousands of people were involved, the riot lasted a long time (six days), it was the first to get major media coverage, and it sparked the formation of many gay rights groups.