John came to New York in 1836 and was ordained to the priesthood by the bishop of that diocese. In 1840 he joined the Redemptorists and became its first member to make a religious profession in the United States. He continued his missionary work in Maryland, Virginia, and Ohio. He was ordained bishop of Philadelphia in 1852 and organized the parochial school system into a diocesan one, increasing the number of pupils within a short time. Many migrants from Europe arrived in the United States at that time and he learned several languages, including Irish, to attend to them. He died suddenly on the 5th of January 1860 and was buried in St. Peter the Apostle Church in Philadelphia. He was canonized by Pope Paul VI in 1977.
His Feast day is celebrated on January 5th and he is the Patron Saint of Immigrants and children.