The Catholic faith first reached Montana through Catholic Iroquois who shared their beliefs with the Flathead tribe. Eager for spiritual guidance, the tribe successfully petitioned St. Louis for a "blackrobe." Jesuit Father Pierre-Jean DeSmet answered the call, celebrating the first Mass in Montana on July 26, 1840. Soon after, dedicated religious orders arrived to establish frontier missions, schools, and hospitals among the Native tribes and early settlers.

As gold rushes and railroads brought waves of pioneers to the West, the Church grew rapidly. In 1904, the Vatican officially split the massive Territory of Montana in half. Western Montana became the Diocese of Helena, and Eastern Montana—covering over 91,000 square miles—became the newly formed Diocese of Great Falls. Bishop Mathias Lenihan was installed as the first bishop, overseeing a rugged frontier diocese.

Throughout the 20th century, the Diocese expanded rapidly thanks to the tireless work of pioneer priests and religious orders. Groups like the Benedictines, Franciscans, Redemptorists, and the Sisters of Humility answered the Bishop's call, traveling to Eastern Montana to staff new parishes, minister to Indigenous communities, and build the Catholic school system that still educates our children today.

To reflect the rapid population growth and regional prominence of the city of Billings, the Vatican officially renamed our territory to the Diocese of Great Falls-Billings in 1980. Today, under the leadership of our eighth bishop, Bishop Jeffrey Fleming, we proudly continue the legacy of those early pioneer missionaries, serving a vibrant flock across the plains and valleys of Eastern Montana.