Devotion to the Virgin of Mercy dates back to the time of the founding of Lima. It is known that the Mercederian friars, who came to Peru with the conquerors, had already built their primitive convent chapel around 1535. This chapel served as Lima's first parish until the construction of the Main Church in 1540. The Mercederians not only evangelized the region, but they also participated in the city's development, building beautiful churches that have been preserved as a valuable cultural and religious patrimony.

With these friars came their celestial patroness, the Virgin of Mercy, a Marian title of the thirteenth century. Tradition has it that around 1218, St. Peter Nolasco and James I, King of Aragon and Catalonia, experienced separately a vision of the Most Holy Virgin who asked them to found a religious order dedicated to rescuing the many Christian captives held by the Moslems. This Order of Our Lady of Mercy, approved as a military order in 1235 by Pope Gregory IX, was able to liberate thousands of Christian prisoners, and later became dedicated to teaching and social work. The Mercederian friars' habit imitates the garments worn by the Virgin when she appeared to the founder of the order. [Our Lady of Our Lady of Mercy] The image of the Virgin of Mercy is dressed all in white: over her long tunic she wears a scapular with the shield of the order imprinted breast high. A cloak covers her shoulders and her long hair is veiled by a fine lace mantilla. Some images have her standing, with the child in her arms, and others with her arms extended showing a royal scepter in her right hand and in the left some open chains, a symbol of liberation. Such is the appearance of the beautiful image venerated in the Basilica of Mercy in the capital of Peru. It was enthroned at the beginning of the XVII century and has been considered the patroness of the capital. In 1730 she was proclaimed "Patroness of the Peruvian Lands" and in 1823 "Patroness of the Armies of the Republic." On the first centennial of the nation's independence, the image was solemnly crowned and received the title of "Grand Marshall of Peru," on September 24, 1921, Feast of Our Lady of Mercy, since then declared a national holiday, when every year the army renders homage to her high military rank.

The image carries numerous decorations granted by the Republic of Peru, its governors and national institutions. In 1970 the town council of Lima gave her the "Keys of the City," and in 1971 the president of the Republic conferred on her the Great Peruvian Cross of Naval Merit, gestures which evidence the affection and devotion of Peru to Our Lady of Mercy, that many consider their national patroness.

http://www.catholicculture.org/culture/liturgicalyear/calendar/day.cfm?date=2014-03-18