In the Catholic Diocese of Aberdeen, Cathedral Church is the main place of worship. It was opened in December 1860 as the essential Catholic Church in the west finish of the city, supplanting St. Peter's Church in the Castlegate, when there were around 1,000 Catholics out of a populace of 74,000 and the quantity of Catholics was increasing. It turned into the Cathedral (the church of the Bishop's Chair) when the post-transformation diocese was set up in 1878. The chief church of the Roman Catholic Diocese of Aberdeen worked in 1860 and designed by Alexander Ellis.