 The Diocese of Greensburg, to which Mount Saint Peter now belongs, was established on March 10, 1951, by Pope Pius XII. Records show that the first Mass in the area was celebrated in the Allegheny Mountains in 1749 by a French priest serving as chaplain to French troops. Demetrius Augustine Gallitzin, the second priest ordained in territories that became the United States, arrived in Loretto, Pennsylvania in 1799. Father Boniface Wimmer came to Latrobe from Germany and established the first Benedictine presence in the region of Saint Vincent in 1846.
