Between 11 February and 16 July 1858, a fourteen year old girl named Bernadette Soubirous, from a poor local family in the town of Lourdes in southwestern France, reported eighteen separate apparitions of a lady at a grotto on the edge of town, a figure Bernadette described in terms that were only later, and gradually, understood by others around her to represent the Virgin Mary. During one of the later apparitions, Bernadette reported the figure identifying herself, in the local dialect, with words later understood as meaning the Immaculate Conception, a title only formally defined as Catholic dogma four years earlier, in 1854, a detail Church authorities later cited as significant given that Bernadette, uneducated in formal theology, was unlikely to have known the term independently.
During the apparitions, Bernadette also reported being directed to a spot where, digging in what had been dry ground, a spring emerged that continues to flow at the site today, and which became central to the devotional and, over time, medical significance the site subsequently acquired.
Local and church authorities initially responded to the reports with considerable skepticism, and Bernadette was questioned repeatedly by both civil and religious officials, but the Catholic Church formally recognized the apparitions as worthy of belief in 1862, and Lourdes developed rapidly afterward into one of the most significant pilgrimage sites in the Catholic world.