WASHINGTON - Legions of demonstrators streamed into downtown Washington on Saturday, bearing flags, angry hand-lettered signs, and their children for one of the biggest local protests so far over police brutality and racial oppression in the United States.

Amid hot and humid weather, people thronged the besieged White House, where authorities used tan military Humvees and dump trucks to cordon off large sections to vehicle traffic.

They gathered at the Lincoln Memorial, where a solitary black man begged white people to see the world through his eyes, and a grandmother told her granddaughter that one day she would be proud she was present.

It was the ninth day of massive protests in the District of Columbia over the death of George Floyd by a Minneapolis police officer, and the Trump administration's militant approach to the unrest that has gripped cities across the country.

Large rallies unfolded across the District throughout the day, from the Lincoln Memorial, to Freedom Plaza, to Capitol Hill.

Demonstrators packed 16th street near the White House, marched along K street, and massed in Chinatown. They spilled onto an interstate highway.

They raised fists and bullhorns, appealed to history, and vowed to be heard.

Lafayette Square, where a heavy security fence blocked any approach to the White House, a block away, was a focal point all day.

The scene of violent confrontations between police and protesters last week, it was now rimmed with a heavy black fence, hung with protest signs, an American flag, and a torn yellow strip of police tape that read: "Crime Scene."

Sixteenth street, which District Mayor Muriel Bowser on Friday renamed "Black Lives Matter Plaza" and had the slogan painted on the asphalt in massive yellow letters, filled with a sea of people as far north as Thomas Circle.

Bowser visited the spot in the afternoon.

"I guess you told Trump about the yellow brick road!" a man called to her as she made her way down the street in a T-shirt and leggings.

Flanked by five security guards sweating in suits, she posed for selfies until the organizer leading the crowd in chants announced her presence: "She's a lady boss!"

"We would like to hear from you," he said, handing the mayor the microphone.

"It is so wonderful to see everybody peacefully protesting - wearing your masks," she began.

She called out the federal police's actions Monday in front of "the people's house," saying that today she "pushed the army away from our city."

To cheers, she spoke of her 2-year-old daughter.

"I want to her grow up in a country where she is not scared to go to the grocery store, not scared to go to work" she said. "Where she can grow up in an America where she can be a senator in the 51st state, Washington D.C."

She ended her two minutes on the microphone with a slogan, ready-made to antagonize President Donald Trump: "Today we say no. In November, we say next."

Across town, at the Lincoln Memorial, a bespectacled black man named Roger Campbell, 30, asked to address a crowd assembled there.

"Excuse me every one," he announced as he turned to face the Washington Monument. "I wrote an article recently and I wanted to read it to everyone if y'all don't mind."

The crowd moved to surround him. Phones and cameras were raised.

"I'm a little nervous," he said.

Someone handed him a megaphone.

He began to tell them how often this week white colleagues and friends had asked: "How can I help?"

"I feel that is a loaded question, due to the various answers I can and would like to give," he said. "You all should try to understand where we as black and brown humans are coming from."

He wiped sweat from his forehead. He spoke of the job interview where he was asked about his hair, the time he cut his dreads for a job, "the talk" his father gave him, which was not about "the birds and the bees."

"It is explained to us that no matter what we do or how far we go in life we will always be viewed as a black or brown person first," he said. "And with that, comes a perception of danger."

He begged the white people around him - who made up around half of the crowd - to ask their black friends instead about their experiences.

"Ask them," he said, "to see the world through their eyes."

When he finished, his voice was cracking and his hands were shaking. A woman with tears soaking her cheeks ran up to hug him.

Nearby, 10-year-old Dakotah Sileshi Mitchell posed begrudgingly on the steps as her grandmother snapped a photo on her phone.

Behind her were about 20 protesters standing silently with signs, yards away from a half dozen military men posted by the monument's pillars.

"You're going to appreciate this when you tell your children you were here," Lisa Wood Mitchell, her 61-year-old grandmother, told her.

"You've been to a lot of marches, haven't you," said Beth Ward, 61, her grandmother's friend and former college roommate.

Dakotah, who is black, wore her hair in tight pigtails as she sat down on the steps and munched on Frosted Mini Wheats.

It was the first day Ward and Wood Mitchell, both longtime District residents, have been able to make it to the protests. Both had to work all week, but have taken part in other ways.

A speaker at the memorial then began to sing the words to 'Lift Ev'ry Voice and Sing,' known as the black national anthem.

Those in the crowd who knew the words joined in song, while others hummed along.

"Sing a song full of the hope that the present has brought us

Facing the rising sun of our new day begun

Let us march on 'til victory is won"

Earlier, Lesley Edmond, 45, who lives in Anacostia, came to the Lafayette Square fence with her son, Reginald Izlar Jr., 10. He wore a blue ball cap and gray T-shirt, emblazoned with the first names of black heroes, "Malcolm, Harriet, Martin, Maya & Frederick."

The White House sat in the distance, as if in a cage, just beyond the equestrian statue of President Andrew Jackson in the square, doffing his hat.

"This is a historic moment, four hundred years in the making," Edmond said. "My son needs to be here. This is a pivotal moment. I've never seen this in my lifetime. Just like I never thought Barack Obama would be president. Until it happened.

"I'm proud to be here, to witness this," she said.

"Also, we're here to protest this president." she said. "His lack of empathy and compassion for the people. His disregard for rule of law. For occupying D.C. We pay taxes. There should not be tanks in the city."

Edmond said they would probably not stay all day. It was already a sticky 80 degrees by 9 a.m., with forecast highs in the mid-90s.

It was her first time at the daily demonstrations, and, because of the virus, only her son's third time out in public. He is fifth-grader at Van Ness Elementary School, near the Navy Yard.

She said she brought him along "to teach him abut his rights - that he has a right to protest . . . to let him see and understand what is going on right now."

Reginald said the killing of George Floyd in police custody scared him.

Asked how he felt about being at the demonstration, he said, "I think more people should be wearing their face masks."

A few blocks north, Tom Reiter walked his dog, Koba, who was wearing cardboard signs reading: "Bring On Your Vicious Dogs."

"I'm a 55-year-old male veteran and I'm just tired of what's coming out of the White House," Reiter said. Indicating his dog, a Japanese Kai Ken breed, he said: "He's tired of it too."

At around 10:15 a.m., a crowd of about 100 protesters peeled away from the White House to march through residential neighborhoods north of the District's downtown area.

They chanted "No justice no peace!" and "Power to the people!" kneeling at intersections far from the centers of power that have been the center of recent protests, urging joggers and people sunbathing in Logan Circle to "March with us!"

Though few joined in, many drivers honked their support, and one man making a delivery on a bicycle raised a fist in solidarity.

T-shirt vendors were doing a brisk business, selling shirts that read, "I can't breathe" across a silhouette of George Floyd's face. Black shirts, blue shirts, yellow shirts, orange, small, large, XL, XXL, all $20 a piece.

Sold by a loose-knit group of District entrepreneurs, the shirts were designed almost instantly after Floyd died.

"Day it happened when he said I can't breathe, it went to print," said Jessie Watkins, 55, who lives in the District.

Watkins said business has been good., selling 17 dozen shirts on one day this week. In preparation for today's march, the group stocked up for another big day.

"A lot of times they put it straight on," said Blaine Proctor, a colleague of Watkins who worked a block away.

Some have bought as many as a dozen shirts to send to relatives, and the vendors are grateful. Even amid the pain, Proctor said, the reality is that the protests have provided his T-shirt business with opportunity that the coronavirus pandemic had taken away.

Typically, the vendors would be traveling across the country selling all sorts of shirts at festivals and other events - but the pandemic ended that.

"Covid-19, it put a stop to everything," said Proctor, who is black. "This is a blessing right here. I'm not saying I'm happy with what happened to George Floyd. I'm not."

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The Washington Post’s Perry Stein, Justin Wm Moyer, Rachel Weiner, Michelle Boorstein, Hannah Natanson and Justin George contributed to this report.