Kammala jumla mai zuwa: A ranar 27 ga Nuwamba, 1911, O'Connell ya zama Archbishop na farko na Boston don zama Cardinal, kuma an ba shi taken Cardinal-Priest na S. Clemente. Ya zo a baya a biyu papal conclaves a jere, a 1914 da kuma
1922, saboda tilastawa ƙetare Tekun Atlantika a cikin jinkirin jigilar ranar. Ya yi gunaguni ga Paparoma Pius XI, wanda ya ba da amsa ya tsawaita lokacin da ke tsakanin mutuwar Paparoma da farkon taron. O'Connell a ƙarshe ya sami damar shiga cikin taron 1939 na gaba, kodayake a wannan lokacin akwai zirga-zirgar jiragen sama.