[2] He was the only son of Francis and Mary (née Goetz) Mundelein, who were of German descent; he had two sisters, Margaret and Catherine.

He attended La Salle Academy and Manhattan College, where he befriended Patrick Hayes (a future cardinal and archbishop of New York).

He received his episcopal consecration on September 21, 1909, from McDonnell, with Bishops Charles H. Colton and John O'Connor serving as co-consecrators, at St. James Cathedral-Basilica.

However, the British government reportedly objected to having a bishop of German ancestry in Chicago, so close to the Canadian border, during World War I.

At a large dinner held at the University Club of Chicago on February 12, 1916, chef Jean Crones slipped arsenic into the soup.

However, the potency of the arsenic was reduced because the kitchen staff was forced to water down soup to accommodate 50 extra guests.

As the diners started exhibiting symptoms of arsenic poisoning, a doctor at the event prepared a makeshift emetic that the victims could drink to promote vomiting.

[14] Simultaneously he gained a voice in city hall, and Catholic William J. Bogan became superintendent of public schools.

[15] Pope Pius XI created Mundelein as cardinal-priest of the Basilica of Santa Maria del Popolo in Rome during the consistory of March 24, 1924.

"[22] In 1935, Mundelein said "that not war, nor famine, nor pestilence have brought so much suffering and pain to the human race, as have hasty, ill-advised marriages, unions entered into without the knowledge, the preparation, the thought even an important commercial contract merits and receives.

[25][26] Quigley Seminary was the site of Mundelein's 1937 "paper hanger" speech, criticizing German Chancellor Adolf Hitler and other Nazi leaders.

[27] He publicly sparred with the Father Charles Coughlin,[28] the Detroit Catholic priest who broadcast anti-banking and anti-Semitic views to millions of radio listeners until he was forced off the air in 1939.