As the visibility and number of American atheists has changed over time, the group has gone through its own struggles over identity. Even today, atheists are significantly more likely to be white, male, and highly educated than the rest of the population, a demographic fact perhaps tied to the long legacy of misogyny and marginalization of women within the movement. At times, nonbelievers have advocated on behalf of minority religious rights and defended immigrants. But they’ve also been among the most vocal American nativists, rallying against Mormons, Catholics, and evangelical Protestants alike.

Schmidt and I discussed the history of atheists in the United States, from the suspicion directed toward them to the suspicions they have cast on others. Our conversation has been edited and condensed for clarity.

Emma Green: There’s a stereotype that the number of nonbelievers is significantly on the rise, along with those who are disaffiliated from religious institutions—often called the “nones.” How do today’s demographics compare with those in earlier American history?

Leigh Schmidt: One of the reasons the nones seem so surprising to us is because we often operate with a Cold War baseline. There really were high rates of religious adherence in in the 1950s. The truism was you had to be a Protestant, a Catholic, or a Jew—you needed that because, in the shadow of this communist threat, it was just a necessary part of American identity. But with the decline of the Cold War we no longer have that hanging over the culture in the same way. I think the nones sometimes look more startling because we’re looking back at that world, when religious membership seemed a part of American citizenship.

With a longer-term perspective, the story is a lot more complicated. When you start getting reliable data in the 1890s census and thereafter, a good 8 or 10 percent of the religious population is actively unaffiliated. And before the 1890s, our data isn’t anything like what we have now. At the time of the Revolution, say, the best guesses on fully paid-up members is like 15 percent of the population. Over this longer term, it’s quite possible that the nones have a lot more company than we often think.

Green: In the late 19th century, what did nonbelievers and religiously unaffiliated people call themselves?

Schmidt: The term “atheist” is a slur. There’s no way anyone in the 17th or 18th century wanted to be called an atheist. It’s a slur within Christian theological discussions about people who are libertines, who are living as if there is no God.

There were other terms that were seen as ways of sidestepping the slur of atheism. You might think of yourself as a freethinker or you might call yourself a deist. But even those were dangerous labels to assume.

Green: Where does the term freethinker come from?