It was, one speaker said, their coming-out moment.

Atheists, non-theists, secularists and others who say they believe in reason, not God, gathered Saturday on the Mall for the first Reason Rally, where they pledged to stand up for their beliefs in a society that they say sometimes views them with skepticism and distrust.

“God is a myth,” said Dave Silverman, president of American Atheists. “Closet atheists, you are not alone.”

Despite intermittent rain, several thousand people gathered on the lawn across from the National Museum of American History to hear a roster of speakers that included comedians, activists and the first openly atheistic member of Congress — Rep. Pete Stark (D-Calif.).

“We’re here,” the crowd yelled in a chant led by Fred Edwords, national director of the United Coalition of Reason. “We’re godless — get used to it.”

Organizers said the aim of the rally was twofold: to unite individuals with similar beliefs and to show the American public that the number of people who don’t believe in God is large and growing.

“We have the numbers to be taken seriously,” said Paul Fidalgo, spokesman for the Center for Inquiry, which promotes scientific method and reasoning and was one of the organizations sponsoring the rally. “We’re not just a tiny fringe group.”

According to the American Religious Identification Survey in 2008, the number of people who claim no specific religious belief was 34 million, 15 percent of the U.S. adult population. A survey by the Pew Forum on Religion and Public Life conducted in 2008 yielded similar numbers.

Saturday’s attendees included a mix of young and old, white, black, Hispanic and Asian. Inside the exhibitor tent, they could speak with representatives of groups ranging from the Society for Humanistic Judaism, a group that embraces the secular roots of Jews, the Hispanic American Freethinkers and Recovering from Religion, a group whose goal is to help people leave their religion.

A small number of counterprotesters stood at the fringes of the rally, holding signs that said, among other things, “Jesus forgives sin” and “Fear God.” Some of them engaged in heated debate with non-believers. One woman, a Reason Rally attendee, approached a group of counterprotesters with a sign on which she’d written, “So many Christians, so few lions.”

Catherine Williams, 13, of Leesburg came to the rally with her mother, Lisa, and brother Nathaniel. She said she attends a small conservative private school where she is the only student who is openly an atheist. Sometimes, she said, it can be uncomfortable because many of her classmates are vocal about their religious beliefs. When talk in the classroom focuses on religion, students turn and look at her for her reaction, she said.

“Coming here makes me feel less alone,” she said, a sentiment echoed by many in Saturday’s crowd.

Dustin Taylor, 21, a student at SUNY Cortland, attracted some attention with his T-shirt, which said: “Free drinks to the person who can prove God exists.”

The student, who plans to become a science teacher, said he wants to ensure that his future students have a strong grounding in science. Too often, he said, people believe something simply because it’s what they’ve been told.

Taylor, along with classmates Erica Deretz and Nick Gardner, recently formed the Secular Student Alliance on the SUNY Cortland campus. The three were in the District for the rally and to take part in the American Atheists National Convention, meeting Sunday and Monday in Bethesda.

Deretz carried a poster with the slogan, “Let’s have a moment of science.”

Matthew Zemo, 29, of Brooklyn said atheists have been too nice for too long. He said he hopes the rally will encourage people to step up and speak out.

“This gathering is long overdue,” he said. “This is just the beginning.”