He emigrated to America in 1888, landed in New York City, and moved to the Territory of Wyoming where he raised sheep in Rawlins.

On December 5, 1929, he was appointed as a Republican to the United States Senate to fill the vacancy caused by the death of Francis E. Warren.

Though Mr. Sullivan was a man of law and order, he did reciprocate the voluntary friendship of outlaws of his day.

In particular, the Wild Bunch aka Hole in the Wall Gang (led by Butch Cassidy and Harry "Sundance Kid" Longabaugh) who respected and were friendly to Mr. Sullivan despite his stand for law and order.

(Denver Post - Sunday Morning Edition, March 9, 1930) Sullivan died on April 8, 1935, in Santa Barbara, California.