The Roman Catholic Diocese of Helena was established on March 7, 1884, and initially included the entire state of Montana. It ... s present boundaries were established on May 18, 1904, when the Diocese of Great Falls (now Great Falls-Billings) was formed from its territory. The diocese covers 51,922 square miles of western and north central Montana, encompassing 21 counties and parts of two others. The diocese’s 57 parishes and 38 missions are structured into six deaneries: Bozeman, Butte, Conrad, Helena, Kalispell, and Missoula. Its diocesan church is the Cathedral of St. Helena, which was dedicated in 1914 and is located in Helena. read more