Read more: History of the Immaculate Conception.
1) The feast of the Immaculate Conception (December 8) was first approved in 1476 by Pope Sixtus IV and extended to the whole Church by Pope St. Pius V in 1568.
2) A commission of 20 theologians, launched by Pope Pius IX to study the issue and issue a final definition, met in 1848. The next year, the pope asked for input from the world's bishops, who responded almost entirely in favor of the doctrine.
3) The formal doctrine of the Immaculate Conception, affirming the freedom of the Blessed Virgin from sin from the very moment of her conception, was proclaimed by Pius IX on Dec. 8, 1854, in the document Ineffabilis Deus. The document included the following statement (translated from the Latin): "We declare, pronounce, and define that the doctrine which holds that the most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Savior of the human race, was preserved free from all stain of original sin, is a doctrine revealed by God and therefore to be believed firmly and constantly by all the faithful." (Read more.)
4) Blessed John Duns Scotus (1266-1308), the much-respected Franciscan philosopher who successfully defended the doctrine of the Immaculate Conception, is also known as Doctor Subtilus, or "The Subtle Doctor." He is also called Doctor Marianus.
5) In her apparitions in both Fatima, Portugal, and Lourdes, France, Mary referenced the Immaculate Conception. To St. Bernadette Soubirous in Lourdes, she identified herself saying, "I am the Immaculate Conception." For more on Marian apparitions, see "Our Lady, Our Guide."
6) St. John Neumann, fourth bishop of Philadelphia and the first (and so far only) canonized American bishop, was invited to Rome by Pope Pius IX in 1854 to take part in the formal definition of the dogma on the Immaculate Conception.
7) Our Lady of the Immaculate Conception is the patroness of the United States.
Source: Information taken from the Encyclopedia of Catholic History (OSV, $39.95).
Gretchen R. Crowe is editor of OSV Newsweekly. Follow her on Twitter @GretchenOSV.