The Juneteenth festivities Joe Greene remembers — some of the first in the area to commemorate the emancipation of the last slaves in the United States — smelled like barbecue, horses and sweat.

Saturday’s celebration of the holiday in Prince George’s County, not far from Greene’s horse farm, was a bit different from the communal barbecues Greene remembers. Vendors sold jerk chicken and cupcakes from food trucks. Instead of the horseback games and rodeo competitions the 80-year-old retiree hosted, families sprawled on the sunny grass at Walker Mill Regional Park and listened to doo-wop and African drumming groups.

Regardless of the modern changes, he said, the meaning behind the celebration remains the same.

“It’s always been about coming together as a community,” Greene said. “It’s about remembering where we came from.”

Juneteenth, named for a combination of “June” and “nineteenth,” commemorates the day the last slaves were freed in the United States. By June 19, 1865, the Emancipation Proclamation already was two years old, the 13th Amendment had been written and the Confederate Army had surrendered. But an estimated 250,000 people remained enslaved in Texas until Union soldiers arrived in Galveston on that date and ordered their freedom.

Donald Cunningham, left, brings his Capital Pool Checkers Club to Walker Mill Regional Park for Juneteenth celebrations in District Heights, Md., on June 18. (J. Lawler Duggan/For The Washington Post)

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Forty-five states, including Maryland and Virginia, and the District officially observe the day, according to the National Juneteenth Observance Foundation. The foundation is part of a growing movement pushing state and national legislators to recognize Juneteenth as an official holiday or national day of observance.

Organized celebrations in Prince George’s County have been sporadic but have been growing in number and popularity, said Dennis Doster, ­black-history program manager at the county’s Department of Parks and Recreation. The department has sponsored a Juneteenth celebration for the past nine years. Attendance has fluctuated, Doster said, but the county expected about 1,000 people to attend this year. The parks department hopes that making Walker Mill Regional Park the annual home to the Juneteenth celebration will help draw bigger crowds.

As families gathered on the lawn in front of the stage just after noon, they began to sway as they joined Wayne Jennings and Louis Davis in traditional call-and-response spirituals.

“The Union is behind us,” the two men sang, beating out a rhythm with a drum.

“We shall not be moved!” the crowd sang back, repeating the refrain that intertwined the verses.

Richard A. Bingham has ­attended Juneteenth celebrations in the area for years and said he is excited to see how awareness of the day has grown. Instead of smaller celebrations in churches and homes, the countywide celebration teaches more people about their shared history and the African American community’s “true day of independence.”

“What to the slave is the Fourth of July?” he asked, quoting an Independence Day speech by Frederick Douglass in 1852 in which the abolitionist argued that while many rejoiced over the nation’s independence, he had to “hear the mournful wail of millions” who were still not free.

Booths dotting the park on Saturday featured exhibits of African and African American history and culture. In a tent near the corner of the field, two young women tirelessly performed a traditional West African dance to modern hip-hop. Every so often, children from the crowd would find the courage to join them, furiously wiggling their hips before running out of the booth, giggling. A nearby tent focused on more recent history, including brightly colored portraits of modern black leaders — the Rev. Martin Luther King Jr., Miles Davis, Billie Holiday and former D.C. mayor Marion Barry — lining the walls.

“It’s so easy to forget all the things these people did,” a woman said to a friend as they browsed the artwork.

In a display showcasing traditional African instruments, Jesse Kirkland, 26, tapped a West African drum, called a djembe. It was his first time attending a Juneteenth celebration, and he was learning the complex history of slavery that he wasn’t taught in school.

“It’s one thing to declare something a reality, to say people are free,” Kirkland said. “It’s another to actually make it reality.”

Along with celebrating a historic moment, Juneteenth also aims to continue the push toward racial equality and “true emancipation,” Bingham said. The freeing of the last slaves in 1865 was not the end of persecution of the black community, he said. He ticked off the injustices: black codes, Jim Crow laws, segregation, lynchings and, more recently, the nine people killed in their Charleston, S.C., church a year ago.

“Juneteenth is a chance to remember, celebrate and reflect,” Bingham said. “But what I focus on is how we can prevent something like slavery from happening again.”