This memorial commemorates the eighteen (18) apparitions of the Blessed Virgin Mary to Saint Bernadette Soubiroux that occurred between 11 February and 16 July of 1858 near the town of Lourdes in the Hautes-Pyrenees region of France. Though there would be other people with her, only Saint Bernadette could see the Lady.
During the 9th appearance, on 25 February, the Lady told Bernadette to drink from a spring that suddenly appeared in the grotto where the apparitions occurred. During the 12th appearance, on 1 March, a visitor washed her arm in water from the spring, and some nerve damage in it was immediately cured. There is a tradition of miraculous cures at the grotto, or received by those who drink or are bathed in its waters. Bernadette later said that the water had no special properties, but it helped focus the faithful who received the cures through faith and prayer.
During the 13th appearance, on 2 March, the Lady told Bernadette to tell local priests that they should build a chapel at the grotto, and have processions to be made to it; the priests were understandably skeptical, but due to the numbers of pilgrims coming to the area, construction of several churches was started within a few years.
During the 16th appearance, on 25 March, the Lady identified herself as "the Immaculate Conception".
Due to the number of people gathering at the site, and making treks to the area, on 8 June 1858, the mayor of Lourdes barricaded the grotto and stationed guards to prevent public access; visitors were fined for kneeling near the grotto or talking about it, and Bernadette saw the last appearance of the Lady from outside the barricade. The grotto was re-opened to the public in October 1858 by order of Emperor Louis Napoleon III, and the pilgrims have not stopped coming since.
February 11 is now celebrated not only as the Memorial of Our Lady of Lourdes but also as World Day of Prayer for the Sick.