In 1858 near the tiny French town of Lourdes, a young peasant girl named Bernadette Soubirous witnessed the Virgin Mary in a grotto. Since then Lourdes has become the most visited shrine in the world, hosting nearly five million pilgrims each year. Historian Ruth Harris traces this shrine's incredible development, placing Lourdes at the center of nineteenth-century debates on religion, science, and medicine that still continue today. She examines the pivotal role of women and children as visionaries, devotees, and advocates, addressing issues of mysticism and nonorthodox faith that speak to our own era of spirituality. Above all, she explores how, at a moment in French history when the Catholic Church was under attack, this place of pilgrimage improbably prospered.