Relita and David Sneed’s son Joshua is only 3, and their daughter Sophia is 1, but the couple believe it is not too early for their children to start learning about the man David Sneed calls “one of the most significant and effective African American leaders in history.”

So on Monday morning, they bundled up the kids and left their Falls Church home to attend the National Museum of African American History and Culture’s annual celebration of the Jan. 15 birthday of the Rev. Martin Luther King Jr.

Standing in the airy atrium as Howard University vocal groups, including the jazz ensemble Afro Blue, performed civil-rights-era classics and original songs and spoken-word pieces, the Sneeds said it was important to teach their children that King’s famous dream is still a work in progress.

Already, their son was brushing up against the United States’ legacy of racism and slavery. “At my 3-year-old’s private school, one of the kids said to another kid, not my son: ‘You’re black, I don’t want to play with black people,’ ” Relita Sneed said. “It still very much affects our lives, and our kids’ lives.”

Around the District, people gathered to contemplate that point and honor the man who has inspired civil rights movements for over half a century. In Ward 8, Mayor Muriel E. Bowser (D) and King’s eldest son, Martin Luther King III, marched in the 39th annual Parade and Peace Walk. Guided tours were led at the King Memorial in West Potomac Park and communities across the region gathered for Day of Service events.

President Trump and Vice President Pence made a brief stop at the King Memorial in the afternoon.

At the African American history museum, adults and children made flags and wrote on sticky notes their own conclusions to the sentence: “Because of Dr. King I can . . . ”

“Eat in all restaurants,” one wrote. “Go to school with white ppl,” wrote another. “Be the best dude possible,” wrote a third.

At a table where visitors tied together swatches of red, turquoise, and gray fleece to make scarves and hats for homeless people, Skai Talbert Darring, 7, of White Plains, Md., sat with her mother and a cousin. It was her first visit to the museum, but she knew a few things about King.

“He got shot at a motel,” she said. “He was coming all the way up to Memphis to help the guys who got smushed in the garbage truck.”

The family visited Memphis recently and saw the motel where King was assassinated, said Skai’s mother, Tawanna Talbert Darring, who home-schools her child. “We thought it would be a good idea to come (to the museum); it’s a good way to get her glimpses of history.”

Visitors could get behind the wheel of a 1940s Buick sedan to learn about the Green Book, a travel guide African Americans used from the 1930s to the 1960s to navigate road trips safely. It listed gas stations, restaurants and motels that were accommodating to black people in a landscape that was often exclusionary or violent.

An interactive feature in the car’s windshield allowed visitors to travel from Chicago to Huntsville, Ala., in 1949, choosing stops listed in the Green Book as friendly or trying their luck with other establishments.

“You all got eyes — we don’t serve your kind; now go home,” said a waitress at a restaurant not listed in the book; a gas station attendant at another unlisted spot told travelers, “Gas and that’s it” — they couldn’t use the restrooms. The Green Book advised people to bring their own blankets, food and a coffee can in which to “do their business,” in case they couldn’t find a bathroom open to nonwhites.

Gary Battel, 70, and Sue Muller, 60, said they had never heard of the Green Book or realized how bad it had been for African American travelers.

“It’s just shocking, to put it mildly,” said Muller, who is white and was raised in Upstate New York. She said she did not remember hearing about the problems encountered by black travelers. “I couldn’t imagine driving today and being afraid of where you stop. It’s a great exhibit.”

Silver Spring resident Laura Meissner, 37, who is white, came with her husband and children, who are 5 and 1. Their family already discusses the history of racism in the United States, she said. “We try to keep it age appropriate, but we don’t want to hide it. We can’t change it if we don’t talk about it.”

Downstairs in the atrium, the Howard singers launched into an a cappella rendition of “Lean On Me.” Relita Sneed held Sophia on her lap and took in the music.

Afterward, she recalled being in the Netherlands, where she grew up as the only black student in her classes, and seeing Barack Obama become the first African American president of the United States.

“I really did look to the U.S. for a lot of things,” she said, adding that since moving here, “I’m more aware of my race. But at the same time I feel like there’s more community here, more celebration and, all the time, more awareness.”

The museum events ran until 4 p.m. About half an hour later, as the sun began to fade, hundreds of visitors were on the plaza at the King Memorial when Secret Service agents abruptly cleared the area.

Trump and Pence appeared on the plaza. They were met with boos, cheers, jeers and a few chants of “USA.”

The men stood before the statue for less than a minute. They bowed their heads, then briefly turned to the crowds and waved.

Michelle Boorstein contributed to this report.