He formed the basis of Father Ferrand, the Ohio-based "Irish by birth, French by ancestry" character in the prologue of Willa Cather's historical novel Death Comes for the Archbishop who goes to Rome asking for a bishop for New Mexico Territory.

His knowledge of the classics helped him take charge of important classes in the college, and at the same time prepare himself for the priesthood by the study of philosophy, theology, and other branches of the ecclesiastical curriculum.

[3] After his ordination, Purcell continued his studies until the autumn of 1827, when he returned to the United States to enter Mount St. Mary's Seminary as professor.

Purcell received notice of his appointment in August 1833, and was consecrated bishop in the cathedral of Baltimore, October 13, 1833, by Archbishop James Whitfield.

Bishops Benedict Joseph Flaget and John Baptist Mary David of Bardstown, Rese of Detroit, and a few priests met him and conducted him to the cathedral, which was on Sycamore Street.

In order to staff the seminary and school, Purcell invited the Jesuit Fathers, to whom he entrusted St. Xavier's Church on Sycamore Street.

Bishop Purcell began constructing a structure built of Dayton limestone, with a spire of solid stone rising to the height of 225 feet.

In 1869, Archbishop Purcell attended the Council of the Vatican, and in the discussion of Papal Infallibility he took the side of the minority which opposed the opportuneness of the decision.

The discussion was to be taken down by shorthand writers, printed after revision by the disputants, and sold, the net proceeds to be distributed equally among Catholic and Protestant charities.

[6] Later that year he created controversy when he invited Gaetano Cardinal Bedini, the emissary of Pope Pius IX, to visit Cincinnati.

[7] Until 1861, Archbishop Purcell condemned slavery only in the "abstract", emphasizing the "prudential motives" that made abolition ill-advised, in his opinion.

[8] However, according to David J. Endres, "Archbishop John Baptist Purcell of Cincinnati was ...the first American Catholic bishop to offer public support for immediate emancipation of slaves.

After 43 years of toil he found the city grown to a population of nearly 300,000, with 40 well-organized parishes having schools giving Catholic education to 20,000 children, a well-equipped seminary, colleges, and charitable institutions to take care of the poor and sick.

In reply to the addresses of congratulation on the occasion, he modestly referred the success to the cordial assistance of the priests and the generous aid of the laity.

The serious financial disaster that clouded his last years came as a result of his natural brother and fellow priest, Father Edward Purcell, as well as the long-lasting effects of the Panic of 1873, also known as the Long Depression.

[10] After 14 years of litigation and mismanagement of assignees, the affair came to an end when the court found the amount due (with compound interest) from the cathedral and diocesan institutions to be $140,000.