The Alabama Freethought Association (AFA) doesn't like the sound of "retreat". They call their convivial annual gathering at Lake Hypatia an "advance". The 2009 schedule promised an atheists vs agnostics softball game, a ceremony honouring atheists in foxholes, paddleboats, music, cartoons, and barbecue.

Lake Hypatia is named for the Alexandrian scientist and philosopher murdered by a Christian mob in 415 CE, who has become an unofficial secular martyr. (There being no official secular martyr-selection procedure.) It's by Talladega National Forest. The state considers it Lake Joan, but the AFA sign on County Road 303 says Lake Hypatia. ("Joan ... of Arc?" I asked. "No, probably the developer's sister.")

Arriving on Friday, I found a registration table in the shade outside Southern Freethought Hall. On one side a cheerful blonde was saying, "I was raised p'lyg." On the other a dark-haired woman marveled, "Until a year ago I never knew an atheist. I thought they were all mean hateful people."

The AFA is a chapter of the Freedom From Religion Foundation (FFRF), based in liberal Madison, Wisconsin. They've been holding the Advance since 1991. It attracts 100-200 people, mostly from the South, many from communities where strong religious norms treat atheism as unthinkable and despicable. At the advance, nonbelief provokes neither shock nor outrage. The 2009 Advance included atheists who were once Black Hebrew, Catholic, Episcopal, Jehovah's Witness, Methodist, Mormon, Pentecostal, Southern Baptist, or United Brethren church members. Or pastors.

Attendees' public expression of nonbelief ranges from Alice Cleveland, an energetic Alabaman who revels in fighting church-state trespasses ("They ought not to have done that!") to – I'll call her "Name Changed" – a thoughtful woman who said, "I live in silence, like my mother did." Her husband said their first advance, last year, had been "the best weekend of our lives."

It's lovely there, with sweet-gum trees, tiny new frogs by the shore, and fireflies in the evenings. As night falls, swallows swooping above the lake gradually give way to bats.

One afternoon a storm threatened. AFA director Pat Cleveland explained which wall to stand against if a siren sounded. I found Edwin Kagin, national legal director of American Atheists, studying the clouds. "There's your headline," he said. "'God Strikes Atheists Dead in Alabama!'"

There was a talk on the evolution of flight in birds. An Oklahoman ACLU director described having her house fire-bombed for suing over school-supported Bible study classes. Songwriter (and ex-preacher) Dan Barker and Pulitzer-winning cartoonist (and ex-Mormon) Steve Benson presented a revue with Barker's songs and Benson's "Jesus Christ" drawings, the ones that make editors say, "Jesus Christ, we can't run that!"

Everywhere people told stories. In scheduled events and between them, over meals and on walks, matters discussed included fleeing a polygamist Mormon sect at 18, trying to still religious doubts by starting one's own church, how you explain beer in the camp refrigerator to Baptist landlords (Yankees left it), winning arguments by quoting the Treaty of Tripoli, getting born-again to impress girls, and scripture-slamming on Chicago buses.

Although they substituted a "moment of bedlam" for a "moment of silence," the advance was no bacchanal. To a San Franciscan accustomed to the Sisters of Perpetual Indulgence, their blasphemy seemed mild. Their T-shirts with atheistic slogans were crisp, probably because they're seldom worn outside the house. As people who had gone through intellectual struggles in comparative isolation, what they really wanted to do was talk. This crowd took great pleasure in reciting the first amendment ("Congress shall make no law respecting the establishment of religion ... ")

On Saturday afternoon Jeremy Hall, just out of the army (and two tours in Iraq), talked about being harassed for his atheism. He also described a nearly fatal encounter with shrapnel in Mosul, when he was at rear gun and the third truck in a convoy was blown up by an IED. "Hey, Hall, close call you had there," said an officer. "Do you believe in Jesus now?" "No sir, but I believe in ballistic glass."

The freethinkers gave Hall a standing ovation. They moved outside to gather at the monument to atheists in foxholes, which has the emblems of the branches of the US armed services engraved on the sides. Fifteen veterans stood around the monument to be honoured by the assembled infidels. The brief ceremony included a recitation of the pledge of allegiance without the inserted "under God" clause.

The group parted wistfully, planning to meet again at Occam's coffeehouse in Memphis, the FFRF conference in Seattle, or next year at Lake Hypatia.