Born in Ireland, Purcell went to the United States for higher education. He studied for the priesthood at Mt. St. Mary's Seminary (where he was later professor and then president) and in France, and was ordained a priest in 1826. He succeeded Edward Fenwick as Bishop of Cincinnati and became archbishop when the see was elevated to archdiocese in 1850. He gained national stature as a Catholic spokesman by his participation in events such as the Purcell-Campbell Debate.