He wrote that Union Army victories were “steps and stages towards eventual ruin” and that they were “matters of humiliation and not of thanksgiving.” Whittingham reacted to Curtis's statements by giving up his pew at Mount Calvary, saying that he did not wish to be “associated with a body so treasonably ungrateful for Divine Mercy shown in the deliverance of the State from armed rebels and thieves.”[3] Curtis gradually became more Catholic in his beliefs and practices.

[2] A final dispute with Whittingham over his pastoral letter on the eucharist prompted Curtis to resign as rector of Mount Calvary in 1871.

In March 1872, Curtis traveled to England to meet in Oxford with Reverend John Henry Newman, himself a former Anglican.

[1][4] Curtis returned to Baltimore later that year, entering St. Charles Seminary in Ellicott City, Maryland.

[4] He then served as Bayley's private secretary and as an assistant rector at the Cathedral of Assumption of the Blessed Virgin Mary in Baltimore.

[2] An accomplished sailor, Curtis enjoyed taking his yawl on long trips down Chesapeake Bay and swimming in the ocean.

[4] [2] During his tenure as bishop, Curtis introduced the Josephite Fathers into the diocese to minister to African American Catholics.

Curtis also built St. Joseph Church in Wilmington, an orphanage, and a parochial school, segregated facilities for the African-American congregation.

[4] Curtis left the diocese with 25,000 Catholics, thirty priests, twenty-two churches and eighteen missions, twelve seminarians, eight religious communities, three academies, nine parochial schools, and three orphanages.

[5] After Curtis's health improved, Leo XIII appointed him as an auxiliary bishop of the Archdiocese of Baltimore in 1897.