[3] He received his episcopal consecration on December 21, 1904, from Archbishop John Keane, with Bishops Richard Scannell and Charles O'Reilly serving as co-consecrators, at St. Raphael's Cathedral.

[3] He was installed on January 31, 1905..[4] In 1904, the Diocese of Helena contained 53 priests, 65 churches, and nine parochial schools to serve 50,000 Catholics.

[7][8] Carroll was a vocal opponent of socialism, which he believed made "no allowance for the development of man's talents, intellectual gifts, his spirit of economy or his ability...Should this policy be pursued it would mean the ruin of a nation.

"[9] He also condemned alcohol as "the most prolific source of poverty and misery"[10] and successfully lobbied the Helena City Council to require bars to close by midnight.

[1] While traveling for his ad limina visit to Rome, Carroll died from a cerebral hemorrhage on November 4, 1925, while in Fribourg, Switzerland.