The massive crowd, bearing flags, banners and placards, then flowed down Constitution Avenue, filling the street, and rallied at the Supreme Court building, across from the Capitol.
"We will not grow weary," Pence said in a 10-minute address to the throng at the monument. "We will not rest until we restore a culture of life in America for ourselves and our posterity."
He said the administration is bent on ending taxpayer funding of abortion and abortion providers. And he said that "next week, President Donald Trump will announce a Supreme Court nominee who will uphold the God-given liberty enshrined in our Constitution in the tradition of the late and great Justice Antonin Scalia."
Scalia, a conservative associate justice of the Supreme Court, died last year.
"Life is winning again in America," said Pence, who added that Trump had asked him to speak at the rally. "That is evident in . . . the historic election of a president . . . who I proudly say stands for the right to life."
Pence was the first U.S. vice president to address the march in its history.
Bundled against a stiff wind, participants from around the country first descended on the northeast grounds of the monument.
Pence, who has called himself an "evangelical Catholic," has long been a hero among antiabortion activists and as governor of Indiana signed what were considered some of the nation's strictest laws on abortion.
Also addressing the crowd was Trump counselor Kellyanne Conway.
"I am a wife, a mother, a Catholic, counselor to the president of the United States of America, and yes, I am pro-life," she said.
"This is a new day, a new dawn, for life," she said.
The right to life "is not a privilege," she said. "It is not a choice. It is God-given. . . . This is a time of incredible promise for the pro-life, pro-adoption movement."
"We hear you," she told the crowd, which earlier was chanting: "Kell-ee-anne! Kell-ee-anne!"
"We see you," she said. "We respect you. And we look forward to working with you."
This year, organizers of the march hoped to see a surge of energy with the election of a president who is expected to move forward on antiabortion policies, including defunding Planned Parenthood and appointing an antiabortion Supreme Court justice.
"He's pro-life," Lynn Ray, coordinator of her Catholic diocese's campus ministry at Louisiana State University at Alexandria, said Friday as she stood on Constitution Avenue with a group from the school. "So that's good for us."
"Being that we're Catholics, we're very pro-life," she said. "Every step we take, we take for an unborn baby. We're not persecuting anyone, of course, just marching for the babies."
Madeline Runyan, 22, a senior at the university, said she, too, is pleased with Trump's stance on abortion. "I'm very confident in what he's doing to help this cause," she said. "I'm really excited and optimistic."
The rally began at about 11:45 a.m. Pence spoke shortly after noon. The march started at around 1 p.m., and the crowd moved east, past the Capitol and toward the Supreme Court, where another large assembly had already gathered.
There were members of the clergy as well as "Bikers for Life."
Many marchers were part of school and church groups, carrying posters – and a life-size cutout of Pope Francis. They sang, chanted and prayed.
Dan Kehoe saw the march not as a political statement but as a religious one.
The 34-year-old from Taos, Missouri, was a chaperon on his daughter's eighth-grade Catholic church trip. They took a Greyhound bus for 22 hours for what they called a "pilgrimage" to Washington.
He saw news coverage of last week's Women's March on Washington and thought that was a political march about women's issues. This event, he said, was "completely different" – not about women's rights but human ones.
"It's not just a woman's choice; it takes two to make a child," he said.
More than 200 people made the trip from his central Missouri church community with him, most of them children. "If the younger generation doesn't speak up now, who will?" Kehoe said.
He said he voted for Trump and is happy with the president's performance so far.
One block-long mass of 200 teenagers from 15 churches and three Catholic high schools filled five charter buses but was only part of a 500-strong group from the Archdiocese of Mobile, Alabama.
"Remember, we are guests in this city, and we're going to be respectful," called Adam Ganucheau, 30, as he and other youth leaders handed out 200 Subway sandwiches. "We are pilgrims; we do not litter."
The size of the crowd was typical, said Ganucheau, who has attended more than a dozen of these annual marches since 2001. But he sensed an extra electricity.
"It's historic that these kids will be able to say they heard and saw the vice president," he said as the throng began to move, sandwiches in hand.
Ganucheau said he is glad to have an antiabortion administration in office, although there are other parts of the Trump agenda that concern him.
In addition to opposing abortion, Ganucheau said, his faith has also led him to support equal wages, equal pay, a welcoming immigration posture and other progressive social causes.
"Being Catholic is more than being conservative or liberal," he said. "We believe in treating all people with respect."
Earlier, Jeanne Mancini, president of the March for Life, listed her four demands for Trump and the Republican-controlled Congress:
– Appoint an antiabortion justice to the Supreme Court.
– Make the Hyde Amendment, which bans federal funding for many abortions in the United States, into a permanent law rather than the one-year provision that has been extended each year since 1976.
– Pass a law banning abortion nationwide after 20 weeks of pregnancy.
– Stop all federal funding for Planned Parenthood unless the organization stops performing abortions.
Nationwide, 57 percent of Americans say abortion should be legal in all or most cases, the highest percentage since 1996, according to a 2016 Pew Research Center poll.
The gathering came a week after Trump's inauguration and followed last Saturday's vast Women's March on Washington.
Asked about the Women's March, Ray, of Deville, Louisiana, said: "I'm all about women's rights, except when it comes to the baby. I believe – it's my opinion – but I believe a baby is a gift from God, and once the baby is a gift from God, it's no longer your body, but there's another body within. And that body has a right also."
When march attendee Brianna Roberts, 21, of Reading, Pennsylvania, met her birth mother two years ago, she said, she was upset to hear that relatives had wanted the woman to abort her.
Her mother was 20 at the time, already had one child and was getting by on food stamps, Roberts said. But when her mother went to a clinic seeking an abortion, she was told she was too far along for the clinic to perform one. So she placed Roberts for adoption.
"She did the right and responsible thing," Roberts said.
Roberts said she did not vote in November because she didn't like either Trump or Hillary Clinton, but she is optimistic that Trump will advance antiabortion policies.
"I thought this was going to be a really big year for policy change," she said.
Francis Leung, 18, a college student from Naples, Florida, said he has attended the March for Life with his parents almost every year since "I was a little kid" in a stroller.
Now, 6 feet tall and a college freshman, he stood in the throng of demonstrators and grinned, saying, "I always look forward to it."
Leung said he grew up in a devoutly Catholic family and has heard a strong antiabortion message from his parents for as long as he can remember.
His nine siblings – eight of whom came to Washington with him this week – have heard it, too.
The march is "a great movement, because it's simple," said Leung, a student at Ave Maria University in Florida. It's simple, he said, because "every unborn child has a right to life."
The first March for Life was held in 1974, one year after the Supreme Court's Roe v. Wade decision, which recognized a right to abortion nationwide. Subsequent marches have taken place on or near the Jan. 22 anniversary every year since.
On Friday, the marchers chanted, "Hey hey, ho ho, Roe v. Wade has got to go!"