On Saturday, officials with Metro, the region’s subway system, said more than 207,000 rides had been taken on the system by 1 p.m., about half of the number by that time during the Women’s March.

A team of crowd science researchers led by G. Keith Still of Manchester Metropolitan University in England estimated that about 180,000 people attended the rally. They examined photographs, video and satellite imagery to estimate the crowd density in different areas of the demonstration. The number is less than half of the 470,000 that Dr. Still estimated had attended the Women’s March in Washington in 2017.

Even so, the streets of Washington were packed on Saturday. Teenagers climbed on each other’s shoulders to reach the bare limbs of trees, where they climbed higher. And each student who spoke drew a cheer that matched, and even eclipsed, the applause given to the musical performers.

Edna Chavez, 17, a high school senior from Los Angeles, said she had lost her brother to gun violence: “He was in high school when he passed away. It was a day like any other day. Sunset down on South Central. You hear pops, thinking they’re fireworks.”

“Ricardo was his name. Can you all say it with me?” she asked. The crowd said his name over and over again, as Ms. Chavez smiled through tears.

Naomi Wadler, the 11-year-old student, introduced herself with a soft “hi” and said she represented the black women who have been victims of gun violence.

“People have said that I am too young to have these thoughts on my own,” she said. “People have said that I am a tool of some nameless adult. It’s not true. My friends and I might still be 11, and we might still be in elementary school, but we know.”

She added, “And we know that we have seven short years until we, too, have the right to vote.”