This feast is celebrated in England and other parts of Europe, not sure if it is as popular in the USA as these countries. Below is from the European Divine Office book’s Proper of Saint’s for the feast of Our Lady of Ransom:
“The only feast of Our Lady proper to England, it reminds us that we are the Dowry of Mary. Originating in Spain for ransoming Christians enslaved by the Moors, devotion to our Lady of Ransom came to express the desire of Catholics to restore her dowry to Mary. Pope Leo XIII personally encouraged the devotion by making this feast proper to all the dioceses of England and by becoming the first President of the Guild of Our Lady of Ransom, founded to foster the reconversion of our country.”
The Blessed Virgin appeared in 1218 in separate visions to St. Peter Nolasco, St. Raymond of Penafort and James, king of Aragon, asking them to found a religious order dedicated to freeing Christian captives from the barbarous Saracens or Moors, who at the time held a great part of Spain. On August 10, 1218, King James established the royal, military and religious Order of our Lady of Ransom (first known as the Order of St. Eulalia, now known as the Mercedarian Order), with the members granted the privilege of wearing his own arms on their breast. Most of the members were knights, and while the clerics recited the divine office in the commanderies, they guarded the coasts and delivered prisoners. This pious work spread everywhere and produced heroes of charity who collected alms for the ransom of Christians, and often gave themselves up in exchange for Christian prisoners. This feast, kept only by the Order, was extended to the whole Church by Innocent XII in the 17th century.