The history of the devotion to the Heart of Mary is connected on many points to the Heart of Jesus; nevertheless, it has its own history. The attention of Christians was early attracted by the love and virtues of the Heart of Mary.

The Gospel itself invited this attention. What was first excited was compassion for the Virgin Mother. It was at the foot of the Cross that the Christian heart first made the acquaintance of the Heart of Mary. Simeon’s prophecy paved the way and furnished the devotion with one of its favourite and most popular representations: the heart pierced with a sword.

But Mary was not merely passive at the foot of the Cross; “she cooperated through charity”, as St. Augustine says, “in the work of redemption”. St. Augustine tells us that she was more blessed in having borne Christ in her heart than having conceived Him in the flesh.

Another Scriptural passage to help in bringing our the devotion was the twice-repeated saying of St. Luke, that Mary kept all the sayings and doings of Jesus in her heart, that there she might ponder over them and live by them. We understand this especially in the Magnificat.

On July 21st, 1855, the Congregation of Rites approved the Office and Mass of the Most Pure Heart of Mary. Now there are at least three feasts of the Heart of Mary:

- that of Rome, observed in many places on the Sunday after the Octave of the Assumption and in others on the third Sunday after Pentecost or in the beginning of July
- that of Père Eudes celebrated among the Eudists and in a number of communities on February 8th; and
- that of Notre-Dame-des-Victoires, solemnized a little before Lent.

However, no feast has as yet been granted to the entire Church.

CATHOLIC ENCYCLOPEDIA: “Devotion To the Heart of Mary.”
http://www.newadvent.org/cathen/0768a.htm