(CNN) Pride these days is synonymous with rainbow-saturated celebrations of the LGBTQ community.

It's easy to forget its solemn origins as a march that commemorated clashes between police and protesters outside a New York gay bar, the Stonewall Inn.

The media coverage of what is now called the Stonewall riots reflected the era's homophobic attitudes. In the late 1960s, it was still illegal in most states to be gay, not a single law protected gay people from discrimination and there were no openly gay politicians or pop culture icons.

In reality, Stonewall galvanized a generation of activists into forming a mass civil rights movement. But many of those people are no longer around to tell us their story of what happened.

To nail down what we know, CNN spoke to three people. David Carter spent 10 years researching and interviewing witnesses for " Stonewall: The Riots That Sparked the Gay Revolution ." Eric Marcus is the creator of the " Making Gay History " podcast, which includes interviews with the late Marsha P. Johnson and Sylvia Rivera, pioneering transgender activists. Robert Bryan joined the crowd outside the Stonewall Inn on June 28, 1969, when a police raid took an unexpected turn.

Here's what they had to say.

What was the Stonewall Inn?

The Stonewall Inn opened as a gay club in 1967 in the heart of Manhattan's bohemian Greenwich Village neighborhood . Despite progressive winds sweeping the nation, New York was notorious for its strict enforcement of anti-homosexual laws that made it risky for gay people to congregate in public, let alone at a bar.

The Mafia stepped in to reap the benefits. To get around state regulations that prohibited gay people from being served alcoholic beverages, mafioso "Fat Tony" Lauria operated the Stonewall Inn as a private club, taking its name from the previous bar-restaurant so he wouldn't have to change the sign.

Stonewall was not the only gay bar in Greenwich Village and it wasn't the nicest. It had no running water and its windows were boarded so no one could see inside. The drinks were watered down and overpriced.

But none of that mattered to patrons because it was one of the few places where they could dance.

Robert Bryan moved to New York in 1968 for the "dancing and cute boys" at Stonewall. He says most of the clientele was like him: gay, white and cisgender.

Robert Bryan in August 1969.

Transgender people were occasional customers, but in that era, they self-identified as drag queens or transvestites, not transgender. And they rarely dressed in full garb, mindful not just of street harassment, but of a law that forbade wearing more than three pieces of clothing associated with the opposite sex.

"At first it was just a gay men's bar. And they didn't allow no women in. And then they started allowing women in. And then they let the drag queens in," Johnson said in an interview in 1979 with Marcus

Because it served gay customers, police raids were common. Management typically bribed police to tip them off in advance so they could turn on the lights and interrupt dancing, which could risk arrest.

But there was no tip the night of the raid that launched the six-day uprising.

How did the riots start?

By the late 1960s, the gay rights movement was building momentum across the United States.

Local chapters of the Mattachine Society , which started in 1950, provided a community for gay men and forums for public discourse. The Daughters of Bilitis , started in 1955, offered a similar support network for lesbians.

The scene outside the Stonewall Inn on July 2, 1969.

They staged pickets in Washington to protest the exclusion of homosexuals from military service, and gathered in Philadelphia each year on July 4 for " annual reminders " demanding legal protections.

Mattachine-New York helped end policies permitting police entrapment . But police raids of bars and bathhouses continued, and a spate of violent homophobic attacks put the LGBTQ community on edge.

On Tuesday, June 24, police raided the Stonewall, rankling patrons who were tired of being harassed. But Deputy Inspector Seymour Pine , commander of the New York Police Department's vice squad, would not back down.

He returned the following Friday with plans to tear up the bar and slap the owners with enough infractions to shut it down for good. Almost immediately, police encountered resistance, Pine later told Carter.

Shortly after midnight, Bryan said he was walking down Christopher Street with a friend when a young man came running.

"They're raiding the Stonewall," he announced.

He joined a crowd gathering across the street in a small plaza. As officers wrestled with a "butch lesbian" who was resisting arrest, Bryan said the crowd threw anything they could get their hands on — coins, bricks, bottles.

The crowd attempts to impede police arrests outside the Stonewall Inn on June 28, 1969.

Police chased rioters through Greenwich Village's streets while Bryan observed a "chorus line" form in front of officers and start chanting.

Carter and Marcus said pictures from the first night show a "rainbow of kids," seemingly street kids and homeless LGBTQ youth, who were likely the main instigators.

What kept the riots going?

Word of the riots spread across the city the next morning. The first night drew 500 to 600 people, but an estimated 2,000 showed up outside the bar on Saturday night.

Members of the crowd held hands in bold displays of public affection. They chanted "gay power," "we want freedom now" and "Christopher Street belongs to the queens."

To block off Christopher Street, they formed a human chain and turned over a car, attracting riot police that led to more clashes.

Amid the melee, a crowd swarmed a taxi and the driver had a heart attack, the only death over six nights.

The next three nights were relatively quiet, likely because people had work the next day.

By the third day of the riots, messages filled a boarded-up window of the Stonewall Inn.

By Wednesday, protesters were back -- inflamed by media coverage of "gay cheerleaders" and "Sunday f-- follies." News of the clashes had also spread to other leftist groups, who saw an opportunity to align themselves with the insurgent movement.

Overall, 21 people were arrested -- most of them on the first night -- and many police and rioters were injured. But a spark was ignited.

What happened next?

The energy from the uprising manifested within weeks.

Weeks later, Mattachine-New York led a "gay power" march from Washington Square Park to Stonewall that drew hundreds of people.

Other Stonewall veterans favored more radical action. A new group that included former Mattachines and feminists anointed themselves the Gay Liberation Front

They held dances to raise money to show they didn't need the Mafia for entertainment. The proceeds funded an underground newspaper, a bail fund for members and lunches for the poor. They questioned mayoral candidates at forums about their views on homosexuality.

The group began to unravel within months. But from its ashes another group formed, the Gay Activist Alliance

Meanwhile, activist Craig Rodwell and his friends came up with another way to harness the energy from Stonewall. He proposed moving the annual July 4 reminder in Philadelphia to New York for the riots' anniversary.

Gay rights supporters rally on the first anniversary of the Stonewall riots.

On June 28, 1970, Rodwell and thousands of people returned to Greenwich Village for the first Christoper Street Liberation Day march . It became an annual event and evolved into the Pride parade, which is marked every year in New York and other cities across the world.

"There were no floats, no music, no boys in briefs. The cops turned their backs on us to convey their disdain, but the masses of people kept carrying signs and banners, chanting and waving to surprised onlookers," Rodwell's partner, Fred Sargent, said of the first march

"It was only after the march that these gay pioneers realized what might be possible."