The Nones have arrived. When asked their religious affiliation, Americans who answer “none” have been on the march for two decades. Now their ascendancy is a fact, confirmed by a Gallup poll showing that, for the first time since 1937 (when Gallup began to ask the question), fewer than half of all Americans—47 percent—belong to a church, synagogue, or other house of worship. As the share of both Catholics and Protestants in the population shrinks, the share of self-identified “nones” grows apace. The most precipitous change has occurred in the two decades between the turn of the present century—when the then-fairly constant figure still stood at approximately 70 percent—and today.