Hundreds of Christians gathered recently in front of the United States Capitol building on a cold and rainy day.

They began a public reading of their holy book, the Bible.

They kept reading for 90 hours.

The event is called the U.S. Capitol Bible Reading Marathon. It marks the National Day of Prayer and has been taking place for 27 years.

Pastor Jeffrey Light of NOVUM Baptist Church in Reva, Virginia spoke to VOA about the event. He said its goal is to show the importance of religion in American life.

"It's foundational for who we are as human beings to know our purpose, and our purpose comes from our creator," Light said.

Few know the part of religion in America better than Alan Cooperman. He leads study of the subject for the Washington-based Pew Research Center.

The center did two major studies on religion in the U.S. in 2007 and 2014. The research found that the American public is growing less religious.

"The percentage of Americans who say they believe in God has dropped a little," Cooperman told VOA. He explained that the percentage of Americans who say they pray daily has dropped, along with the percentage who say they go to religious services at least once a month.

Cooperman said the share of Americans who do not identify with any religion has been rising very quickly.

In his words, "It's gone from 7 percent in 2000, 16 percent in 2007, to 23 percent overall today."

Cooperman believes the drop in religious involvement reflects a generational change. Young Americans are growing into adulthood with looser ties to religion. The children of today are also less involved in religious activities than the children of past generations.

Religion and politics

But lawmakers and government officials are more likely to be religious than the general public. Organized faith appears to still play an important part in U.S. politics.

More than 90 percent of the United States Congress is Christian compared to 70 percent of the general public. At a recent Senate discussion, members of Congress talked about how they balance faith and politics.

Senator James Lankford is a Republican from Oklahoma. He told VOA that faith is "the lens" he looks through.

He added, "If it's a faith, it affects everything."

Many religions are represented in Congress. Along with Christian legislators are Muslims, Hindus and Jews. There are also some atheist lawmakers.

‘Overwhelmingly religious'

For Cooperman, even the increasing number non-religious Americans may not be enough to change the role of faith in American life and politics.

"...the American public remains overwhelmingly religious," he said. In his words, "It's a very religious country. Three quarters of Americans, about 77 percent of the population, still identify with a religious group."

Pastor Jeffrey Light agrees. He said the role of religion will continue to play an important part in this year's presidential election.

"For me and those that are seekers of the word of God," he said, "we will certainly seek a leader who honors God."

I'm Caty Weaver.

Yang Chen and Adrianna Zhang wrote this story for VOANews. Jim Dresbach adapted it for Learning English. Caty Weaver was the editor.