The American Catholic Historical Society (ACHS) is a historical society based at 263 South Fourth Street, Philadelphia, Pennsylvania. Founded in 1884, it is the oldest Catholic historical society in the United States. The goal of the society is to collect, research, and maintain historical records relating to the contribution of the Catholic Church to American society and culture.
The American Catholic Historical Society was founded in response to Pope Leo XIII's 1883 pastoral letter on historical studies, Saepenumero considerantes.[1] The society was organized on July 22, 1884, received the blessing of the pope on January 10, 1886, and formally approved by the Archbishop of Philadelphia, Patrick John Ryan, on September 6, 1886.[2]
The Catholic Historical Research Center of the Roman Catholic Archdiocese of Philadelphia houses the society's manuscript collections.