The Archconfraternity of the Misericordia, previously the Company of Santa Maria and earlier still the Militia of Santa Maria, was founded in the 13th century, during the period of the really ferocious battles between the Guelphs and Ghibellines for the control of the government of the Republic. However its development was also linked to the battle of the Church against the "Patarine" heretics, who were instead supported by the Ghibellines to weaken the papacy. The Dominican monk, St. Peter the Martyr, founded the Militia of Santa Maria (1224) as a protection against the Patarines.
Apart from its armed defence of the Faith, it soon found itself carrying out other tasks, like assistance to the needy, burial of the poor and donations of dowries to poor girls. The City Council of Florence raised the confraternity to the rank of public board, with the power to elect its own Captains, on March 31st 1329. A group of auxilaries was created who had the exclusive task of the transport of the sick, which they did using a "zane", a sort of stretcher in the shape of a basket that was attached to the back with straps. The "zane" was later abandoned for the "cataletto" or shoulder litter which, in its turn, and for many centuries, made way for the hand cart (the first ambulance car was to arrive in 1911). In the meantime the Confraternity of the Misericordia built its headquarters (1352-58) opposite the Baptistery, in the Loggia on the corner between Piazza San Giovanni and Via Calzaiuoli; it merged (1425) for a while with the Company of the Bigallo until their separation in 1490. It also changed the colour of its robes from red to black (1497) and set up its permanent headquarters (1576) in a palace that was donated by the Grand Duke Francesco I de' Medici and stood on the opposite corner of Via Calzaiuoli, facing Giotto's Belltower.

The palace contains a great many works of art, among them a 13th century Crucifix, a St. Sebastian and an unfinished Madonna (1495-97), carved by Benedetto da Maiano. A painting by Pietro Annigoni can be seen on the exterior facade. The patron saint of the confraternity, St. Sebastian (its other patron saint is Tobias), is celebrated here on February 20th each year with the distribution of blessed bread.
Even today the Archconfraternity of the Misericordia continues to give assistance to the sick and needy and Florentine pride likes to think that this institution later inspired Florence Nightingale (who was English but born in Florence) to create the Red Cross.