The Arch-confraternity originated from the Company of the Oblates and Brothers of the Misericordia for the Poor in Christ. It was founded in Siena in 1250 and, after alternating vicissitudes, suppressed in 1785 through a decree of Grand Duke Peter Leopold of Lorraine. In 1835 the Siena Arch-confraternity of the Misericordia was affiliated with that of Florence. The congregation's medical collection includes interesting stretchers and litters from the 19th century, which bear witness to the activity carried out by the Brothers and the equipment they used.