Horns blared, fireworks exploded, and shouts of triumph filled the air as supporters of Joe Biden and Sen. Kamala D. Harris (D-Calif.) spilled into the streets of Washington and its suburbs Saturday to celebrate the announcement that the pair had won the 2020 presidential election. As the day unfolded, thousands descended on the White House — which had been the scene of months of tense protests this year over racial injustice and inequality — to dance, sing and revel in a victory that some worried would never come, while smaller groups of more subdued Trump supporters gathered at the Washington Monument and in front of the Supreme Court.

On a glorious fall morning, the announcement of Biden’s win was news the region, which voted overwhelmingly for him in the presidential contest, had been desperate to hear — and it responded with a cacophony of clanging pots and pans, joyous whoops and the popping of corks on thousands of bottles of champagne that had been purchased with just this moment in mind.

Around noon, just after the election was called by news outlets, an impromptu parade broke out on the streets of the nation’s capital to celebrate Biden’s victory. A brass band perched on the back of a truck played upbeat jazz as people spilled out of homes, shops and restaurants in downtown D.C. to join the march.

The crowd swelled quickly as the truck moved from the heart of Adams Morgan in the direction of the White House — first a dozen, then three dozen and soon close to a hundred. A few police officers on motorcycles escorted the group as passing cars stopped to honk, their drivers cheering.

Celebrations erupted across the city. Cheers and clapping filled the air outside Eastern Market on Capitol Hill. A few blocks away near Third Street and Pennsylvania Avenue SE, “The Star-Spangled Banner” blasted from speakers on a repeated loop.

A woman on a bicycle pedaled through Columbia Heights shouting, “It’s over!”

A man in Shaw stood on the curb with a stemmed glass of red wine, raising it to passersby. “We won!” he shouted in Spanish. “We won!”

In a Silver Spring neighborhood, a family rented a soft-serve truck and invited everyone over for victory ice cream.

Residents of the leafy, quiet streets of upper Northwest Washington, where the Halloween decorations featured Biden-Harris signs and “Vote” themes, rushed to Connecticut Avenue to cheer, whoop and ring cowbells as cars and trucks drove by with signs hailing the election of the Democratic ticket.

Parents waved small American flags and held their children on their shoulders, and even a recycling truck blared its horn as scores of vehicles headed south on Connecticut Avenue toward the White House.

The spontaneous celebrations around the region were not surprising given how residents had strongly supported the Biden-Harris ticket. Ninety-three percent of District voters selected Biden. He won 63 percent of Maryland voters and 54 percent of Virginia voters but did better in both of those states in counties adjacent to the District.

As the jubilant crowds gathered in Washington, similar scenes unfolded in many cities and towns across America, particularly those in states such as Pennsylvania, New York, California, Michigan, Wisconsin, Nevada and Georgia that helped deliver Biden’s electoral victory.

Street parties and honking horn fests erupted all over the region Saturday, but for thousands of Washingtonians, the main celebration was at the fenced-off White House, the scene of months of tense protests this year over racial injustice and inequality. They walked, biked and scootered there in droves all day long to express their joy with the result and send an emphatic message to President Trump that his time in office was soon to end.

In the accessible blocks closest to the White House, drivers stuck their heads out of car windows and waved Biden flags. Cyclists cheered as they sailed past, lifting fists in the air. Along 15th Street NW, where protesters had so many times marched against the outgoing president, a young Black woman stuck her head above the sunroof of her car, yelling: “Finally!”

A Metro bus driver stopped her bus at the corner of 16th and I streets NW to take a video of herself dancing with the White House in the background. Cars in gridlocked traffic honked in support, and people passing by started dancing along with her.

Hundreds of people had flocked to the fence around Lafayette Square to celebrate the victory announcement. They wore masks that said “vote” and Biden-Harris 2020 shirts. Some carried signs declaring “When we count, democracy wins!”

As the champagne sprayed and “Sweet Caroline” blared, Dasia James and Thema Thomas began to dance in the middle of Black Lives Matter Plaza.

The 23-year-old graduates of Howard University were elated that their country had elected Harris, a Black woman and fellow HBCU alum, as vice president.

“This is not just Kamala’s win,” James said. “It’s a win for all Black women, especially those who fought to get voters registered in key states.”

While the vast majority of those on the District’s streets Saturday celebrated the election news, a number expressed their displeasure with the result.

Waving American flags and Trump 2020 banners, more than 100 Trump supporters gathered at the base of the Washington Monument, chanting “four more years” and “stop the fraud!”

Many stood maskless, wearing red Make America Great Again caps.

The group soon attracted the attention of the Biden supporters who had been enjoying picnics, ice cream and freshly popped bottles of champagne in the grass below.

They brandished signs that said “You’re fired!” and “Biden Harris 2020.” Some began to dance to the music of Stevie Wonder pouring forth from a portable microphone.

Outside of Trump National Golf Club in Sterling, Va., where Trump golfed Saturday morning, scores of Trump and Biden supporters gathered after the race was called.

The two groups were separated by a highway median and acted peacefully aside from some occasional shouting. Vehicles, including pickups and Jeeps with Trump flags, drove back and forth, horns blaring. The Biden supporters were cheering; the Trump supporters were more subdued.

The president returned to the White House Saturday midafternoon, with Secret Service agents and D.C. police blocking off the intersection of E and 18th streets NW, stopping cars and telling pedestrians to move onto the pavement. As Trump’s motorcade went by, the several hundred people gathered there to celebrate released a unified cry: “Boooo!”

Some gave the passing cars a thumbs down; others raised their middle fingers. A group of young women yelled “bye!” — hoping their message would get to the president. Once the motorcade passed, there was a beat of silence before the cheering and dancing started up again.

Another Trump property, the Trump hotel on Pennsylvania Avenue NW, became a scene of beeping horns, middle-finger waves and many expletive-laced goodbyes.

Michelle Saksena, 36, stopped in front of the Trump hotel to take a picture of it to text to her friends. Over the photo, she wrote, “Out of business.”

She was thinking about what it meant that a half-Indian woman, just like her, would be the second-most powerful person in America.

“I remember when I first heard about her, my dad, who is Indian, said you have to pronounce her name right!” she said. “I feel . . . I just feel safer, knowing she’s there.”

At 73, Carla Yates Bremer was among the older people who had decided to gather outside the White House on Saturday. Dressed in a silk blouse, a white KN95 mask and black capri pants, she stood feet from the black fence, watching the crowd of young revelers dance, spray champagne and cheer.

“This is a day I’ve been waiting for for four years,” she said.

As an older person, Yates Bremer said she was aware of the possible risk of getting the coronavirus in the crowd but pointed out that everyone around her was wearing masks.

“This is the people’s house. And now we’ve got it back,” she said.

A young man scaling a black lamppost started spraying the crowd with champagne, eliciting cheers. Yates Bremer didn’t flinch; she put her hand out to touch the droplets coming down and laughed.

Tina Matthew, an independent consultant in Maryland, was celebrating for two people on Saturday. For herself, a Black woman tired of living in a divided nation. And for her late friend, a nurse in Chicago who died of the novel coronavirus. A record 128,000 new coronavirus infections were reported in the United States on Friday.

“I have been thinking about my friend and her kids and the fact that if the information was out there and correct, maybe she would have been out here celebrating with us,” Matthew said, standing on the edge of Black Lives Matter Plaza by St. John’s Church. “But this is a step in the right direction.”

Cole Bockenfeld, 34, was among the parents who brought their children to the celebration outside the White House Saturday. A Senate staffer, Bockenfeld said he loved living in D.C. for these moments — a front-row seat to history, he said. He was out in the streets when Barack Obama won in 2008, he stood in the cold during the Women’s March, and he protested this summer in support of Black lives.

Bockenfeld is White. His wife is Black. He wanted his daughter, 10-year-old Aliya, to witness this — the shift in the political climate, the first time in U.S. history that a woman had been elected to the White House.

“It’s great to have that role model,” Bockenfeld said, squeezing his daughter’s shoulders and growing emotional. “You can have anything; you can do anything. It’s not a hypothetical.”

In Lincoln Park, the election results turned an unseasonably warm and somewhat sleepy Saturday afternoon into something electric.

“Another One Bites the Dust” blared from a speaker as cars circled the park on Capitol Hill, honking in support of Biden. A dozen people doing downward dog on their yoga mats looked up as a young man rode by on a bicycle with a “Biden 2020” sign, whooping in delight. The sound of a champagne cork popping capped the sudden shift in mood.

Sarah Raker poured celebratory glasses of bubbly for her and her friend, Emma Trachman. After voting for Biden on Tuesday, the 28-year-olds had felt their stomachs drop as Trump initially surged ahead. After three days glued to their television screens, they had begun to feel more hopeful on Friday as Biden moved ahead in several key undecided states. They were walking to the park on Saturday morning when a group of movers began screaming and cheering. Raker began to cry.

When the tears stopped, the friends bought a bottle of champagne at a nearby store and sat on a rainbow-colored blanket, feeling happier than they had in a long time.

The two were thinking about going to the White House. But first, Raker said, “there will probably be more champagne.”

By 8:30 p.m., after more than eight hours of celebrations, Black Lives Matter Plaza was still filled with hundreds of people.

In front of the White House, where revelers had spent hours cheering, chanting and singing, the crowd quieted some as Harris’s speech began. People of all ages and races huddled over their phone screens. Her words played through a speaker in the middle of the gathering.

Tears began to stream down Angelique McKenna’s cheeks as Harris invoked the other women — Black women — on whose shoulders she says she stands.

McKenna, 25, a Black woman from Arlington, voted for Biden in the second presidential election of her adult life. She said seeing Biden and Harris win has meant more to her than she “could have imagined.”

“There is going to be a Black woman vice president of the United States — and no one, no one, can take that away from us,” she said. “I believe Kamala will fight for equality for us, for all people.”

“You marched and organized,” Harris said in her speech, and in the location where much of that marching happened, the people cheered. They hollered when she mentioned Jill Biden and talked about the sacrifices of women of color.

But the loudest eruption came when Harris said “you chose Joe Biden.”

As she spoke of a country of possibilities, fireworks ignited above the crowd.

Though the people listening couldn’t see Biden run onto the stage, they went wild just the same, chanting “USA, USA, USA!”

As Biden spoke, a “Happy Retirement” balloon floated above the crowd. The pavement was littered with smashed beer cans and champagne corks. A father held his daughter on his shoulders. A mixed-race couple held each other and held American flags.

When one of the speakers broadcasting Biden’s address stopped working, the crowd migrated toward another speaker near St. John’s Episcopal Church, straining to hear.

In the same spot where Trump stood this summer after protestors were cleared with tear gas, the crowd cheered as Biden said, “This is our time to heal in America.”

Victoria Benning, Emily Davies, Katie Mettler, Michael E. Miller, Hannah Natanson, Samantha Schmidt, Susan Svrluga, Rebecca Tan, Rachel Weiner, Debbi Wilgoren and Clarence Williams contributed to this report.