 On November 26, 1935, O'Hara was appointed the ninth Bishop of Savannah, Georgia, succeeding the retiring Bishop Michael Joseph Keyes.During his tenure, he erected the Cathedral of Christ the King in Atlanta, which was dedicated by Cardinal Dougherty in January 1939.The cathedral was built on the former site of Ku Klux Klan gatherings, and O'Hara even invited Imperial Wizard Hiram Wesley Evans to the dedication.