Weather permitting, a new billboard will be mounted along Interstate 26 on Monday displaying a succinct message superimposed against a blue sky: "Don't believe in God? You are not alone."

The billboard is part of an advertising campaign sponsored by the American Humanists Association and the Secular Humanists of the Lowcountry.

"In the past, some individuals have taken offense at this message," Secular Humanists Vice President Herb Silverman said in a statement. "But that isn't our purpose. Rather, it is to introduce like-minded people to the Secular Humanists of the Lowcountry as well as to let others know that it's OK to be openly nonreligious."

The campaign has been under way throughout 2008, with billboards appearing in New York City, Philadelphia, Denver and Colorado Springs, Colo., according to Fred Edwords, director of communications at the Washington-based American Humanists Association. In the nation's capital, where billboards are outlawed, the organization mounted its message on buses, prompting controversy, though most of the criticism came from outside the area, Edwords said.

The billboard along I-26 near Spruill Avenue is the campaign's first foray into the South, he said.

"The response has been generally positive because (the billboard campaign) basically addresses those who already don't believe in God," Edwords said. "It's not an attack on other people's religion."

The purpose is to show nonbelievers that they're not alone and that there is no shame in leading a purely secular life, he said.

The American Humanists Association has 120 local chapters, many of which have seen their membership grow in recent years, Edwords said. Atheists and agnostics increasingly are emerging from the woodwork in part because a nontheistic worldview has gained legitimacy thanks to recent books, movies, blogs and Web sites, he said.

President Barack Obama in his inaugural address included "nonbelievers" when he referred to the composition of the U.S. and the need for all its citizens to work together. It was the first time a modern U.S. president acknowledged this group in a public address.

Recent surveys show that as many as 15 percent of Americans consider themselves nontheistic or unaffiliated with any organized religion.