By Dan Merica, CNN

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(CNN) - Todd Stiefel is far from a household name, and the odds he gets recognized on a street corner, even in his hometown of Raleigh, North Carolina, are small.

For Stiefel, a slim, scruffy ex-Catholic, his public persona is his wallet and activism. Through the Stiefel Freethought Foundation, the 38-year-old has made an indelible impact on the nation’s fastest-growing “religious” group: the nonbelievers. Most of the highest-profile atheists campaigns –- flashy billboards in high-traffic areas, news-making efforts to get atheists to come out of the closet, and boisterous rallies - are funded by his fortune.

Stiefel isn’t shy about his far-reaching goals.

“What I am trying to accomplish is multifold, he told CNN. “I consider myself working on the next civil equality movement, just like women’s rights, LGBT rights and African-American Civil Rights. We are still in the early stages of eliminating discrimination against atheists and humanists. That is something I really want to accomplish.”

So far, Stiefel has pumped $3.5 million into those aspirations, and his money benefits a number of atheist organizations, from the Clergy Project, a group that helps atheist and doubting clergy out of the closet, to American Atheists, arguably the most in-your-face atheist group in the country.

Stiefel sees his work as far more than just money. For him, this is just the beginning.

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From Catholic school to atheist millionaire

Stiefel was born in Albany, New York, in 1974 to Catholic parents. He was raised in a Catholic household, confirmed in the church, attended Sunday school, went to a Catholic high school.

“I was a cross-wearing, praying, religious-retreat Catholic,” Stiefel said. “You could say there were points that I felt the spirit.”

But his faith, he said, fluctuated during high school. “I was always a skeptic,” he said, “and I always asked a lot of questions.”

At 18, Stiefel attended Duke University to pursue a degree in psychology. To fill an elective, he took an Old Testament history class at the Duke University Divinity School. It was there, he said, that his final “ebb” away from belief took hold.

In the class, Stiefel said he saw a flawed logic in the Old Testament. In particular, he said, he began to see much of the Old Testament as unoriginal stories that had been told in many pagan traditions.

“'Wait a second, is what I believe in really the truth or is it really the accumulation of myths bundled in a package?’” Stiefel remembers asking himself. “That was the end of my faith right there.”

After graduating from Duke, Stiefel went into the family business: Stiefel Laboratories, a company that develops products to combat skin diseases. For 12 years, Stiefel worked with his family and turned the business into a major player in their specialized market.

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In 2009, with Stiefel in an executive position, the Stiefel family opted to sell the company to GlaxoSmithKline. The price tag: $2.9 billion, according to media reports at the time.

“I only got a very small piece of that, for the record,” Stiefel said with a laugh. “I did, however, find myself in a unique and fortunate position where I was able to do whatever I wanted to do.”

And like many who have the luxury of doing exactly what they want, Stiefel began thinking about what he was truly passionate about. After kicking around the idea of starting another business, the answer became clear to the young millionaire: advocating for atheism.

“I wanted to try to help the world,” he said. “I wanted to give back and this seemed like the most productive way to help humanity.”

‘Just doing my part’

Stiefel put $2 million in to begin his foundation. In his first year, according to tax documents, the nonprofit disbursed $700,000 to groups like the Secular Coalition for America, the American Humanist Association and Americans United for Separation of Church and State.

In 2010 and 2011, the giving continued with the foundation distributing around $750,000 to different atheist and humanist causes. In 2011, he also pumped another $500,000 into his foundation.

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“I am just doing my part within my means,” he said. “Different people have different means. I am doing what I can do, just like the rest of the people in the movement are.”

But recipients of the money, such as David Silverman, president of the American Atheists, see his impact as much greater than just a one-off activist.

“Todd is an example of what major contributions can accomplish for atheism,” he said. “From a donation stand point, he is really leading the movement to a different level.”

Walking the line

One of Stiefel’s major concerted contributions in the last three years was the Reason Rally, an event held on the National Mall in Washington, which was billed as a watershed moment in the atheism movement. The goal of the event was to show to religious Americans that atheism was a powerful minority in American life.

The rally drew a number of high-profile speakers, including Richard Dawkins, the author of “The God Delusion,” and thousands of attendees, despite rainy weather.

In his speech to the crowd, Stiefel talked about what he sees as the most important problem facing atheism: “Discrimination comes from ignorance, and in this case it is ignorance about our beliefs,” he said. “We are told freethinkers believe in nothing, but that’s a misunderstanding. We believe in a lot of things; we don’t all believe the same things.”

Stiefel put $250,000 toward the rally, a contribution that Silverman, the organizer, said was critical.

“He brought the Reason Rally to a brand new level,” Silverman said. Without that money, “we would have had far fewer people and a far smaller event.”

Silverman and the Reason Rally advocated for a specific brand of atheism. Silverman, who regularly calls his group the “Marines of the Freethought Movement,” is not shy in making it clear that he views his goal in calling out religion and elevating atheism.

Stiefel says he doesn't necessarily endorse those tactics wholly, but he does see their validity.

“I try to walk a line,” he said. “I see religious criticism as valuable, and groups like American Atheists are good at that. I do think we have to have a dialogue about who has the right ideas and part of that is pointing out the flaws in religious ideas.”

Stiefel continued: “I also see inter-belief work, though. I do find a lot of value in inter-belief work and I do see a lot of value in general charity work.”

Evidence of that is his work on cancer fundraising.

In 2012, Stiefel approached the Foundation Beyond Belief with an idea of creating networks of nonbelievers around the country to help raise money for the Leukemia & Lymphoma Society. Stiefel tapped into his atheist network and began organizing different event.

In total, the atheist groups raised $430,000 in 2012, including a $215,000 donation from Stiefel and his wife, Diana.

“Across the country there are 150 local groups of atheists and freethinkers raising money for charity,” Stiefel said proudly.

The key, however, was bridging the gap between atheist and religious communities in the name of charity.

“We welcomed Christians, as well,” he said. “Some of our biggest fundraisers were Christians.”

For 2013, the goal is to raise $500,000.

Expanding the community

With money and resolve comes great influence for Stiefel. He has the ear of many atheist leaders, meaning he can dictate the movement’s focus.

Stiefel said he wants to see the atheism movement expand its footprint.

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“What I would really like to see is expanding out communities to people who may not just be atheists or agnostics and into people who are religiously skeptical and may still have some religious beliefs,” he said. “Nobody is a perfect skeptic and I would like to see more people like that in our community.”

For Stiefel, this is a personal priority. He says his wife, whom he describes as a skeptical Christian, is someone who would fall within an expanded atheist movement.

“My message is not only of anti-theism,” Stiefel said. “I don’t choose to attack religion itself. I see religion as something that provides both good and ill to the world.”