Eight years ago, a handful of Roman Catholic families in Huntersville, a suburb of Charlotte, N.C., started a new parish. The home of their church, St. Mark, was a bowling alley. Our Lady of the Lanes, as they jokingly called it, was an apt symbol of the scarcity--and supple ingenuity--of Catholics in a region known as the buckle of the Protestant Bible Belt. Soon St. Mark was gaining a family a day. Now its almost 2,800 families hear Mass in a cavernous gymnasium as they await completion of a new church. Among the newcomers is Ben Liuzzo, 54, a financial-services...