A Cathedral is a church that contains the Bishop's Chair or "cathedra" which is symbolic of the bishop's teaching ministry. The cathedral generally has a staff of clergy presided over by the Dean and assisted by clergy called Canons. Together, with the laity, they carry out a program which includes worship, pastoral work, teaching, and outreach. The cathedral is also available for many diocesan activities and is the principal church in which the bishop presides on special occasions. St. Mark's was the cathedral for the Missionary District of Western Nebraska until that diocese merged with the Diocese of Nebraska in 1946. As a part of that merger, it was insisted that St. Mark's retain its designation as pro-cathedral, representing the history and missionary culture of the western part of the Diocese.