He subsequently resigned from this position to join a group of priests conducting parish missions in the Archdiocese of Lyon.

Loras was appointed vicar general for the Diocese of Mobile and assigned the task of completing the training of the seminarians who had accompanied Portier to America.

He was also named rector of the Cathedral of the Immaculate Conception in Mobile, and held these positions for seven years,[2] helping Portier recruit priests to serve the diocese.

[3] In 1837, the third Provincial Council of Baltimore recommended to the pope that new dioceses be created due to the expansion of the United States.

Pope Gregory XVI established the Diocese of Dubuque on July 28, 1837, and Loras was named its first bishop.

The principal co-consecrator was the bishops Antoine Blanc of New Orleans,[2] assisted by John Stephen Bazin of Vincennes.

The diocesan territory consisted of present-day Iowa, most of Minnesota, and North and South Dakota east of the Missouri River.

Upon returning, he spent the late winter and early spring in St. Louis waiting for more favorable conditions to travel to Dubuque.

He brought with him Joseph Crétin, who was consecrated first Bishop of St. Paul in 1851, Jean-Antoine-Marie Pelamourgues, who would spend his career in the diocese based at St. Anthony's Church in Davenport, and seminarians Augustin Ravoux who would become a noted missionary among the Native Americans,[5] Lucien Galtier, Remigius Petiot, and James Causse who were pioneer priests in Minnesota.

In 1846 when Loras discovered German Catholic immigrants thirty miles west of Dubuque, he convinced them to name their community New Vienna in honor of the Austrian capital and home of one of his benefactors.

[7] Loras visited Mount Melleray Abbey in Ireland in 1849 and expressed his desire to have the Trappists establish a monastery in his diocese.

The new school, renamed St. Bernard's College and Seminary, was plagued with financial problems but managed to survive until Loras' death.

The Irish felt slighted when Loras provided the Germans with their parish, Holy Trinity (now Saint Mary's).

Around 11:00 PM, his housekeeper heard Loras moaning and informed Father McCabe, who proceeded to the Bishop's room and found him collapsed on the floor.

[9] At the time of his death, the Diocese of Dubuque had grown to 54,000 Catholics, in 60 parishes, served by 48 priests in a territory that now only covered the state of Iowa.