Dotting many U.S. main streets are the steeples and towers of beautiful and historic buildings, originally built as houses of worship. From its founding, mainline denominations gave America a kind of Protestant consensus, much of our nation’s charity, many of its most prestigious schools, and a significant number of congressional leaders and even presidents. Today, many of these buildings, especially those draped with rainbow flags, lie empty. On Sundays, only a small number of worshipers, mostly white and grey-haired, sit in the pews.