Mahoney was born to an Irish Catholic family in Chicago in 1925 and grew up in Englewood. He attended Visitation Grammar School and enrolled at what was then called St. Ignatius High School in 1939.

Mahoney would have graduated with the class of 1943, but withdrew from school on December 17, 1941 - ten days after Pearl Harbor. 

Mahoney enlisted in the U.S. Army and was sent to Europe to serve in an Anti-Tank Company. He was stationed in Northeastern France when German forces launched a counteroffensive in late December of 1944. 

Jeremiah Mahoney was killed in fighting sometime on January 17, 1945. The intensity of the fighting necessitated an evacuation from the area and his unit was unable to recover his remains. Mahoney was just nineteen years old when he died.

A notice of Mahoney's death was posted in the Alumni Servicemen Newsletters in March of 1945: "Official notification of the death of Jeremiah Mahoney '43 was released by the War Department late in January. Jerry was killed in France. A letter from one of his pals states: 'Mahoney was digging a dugout or foxhole with another soldier and shells kept falling. One came close and the fellow jumped into the hole on top of Mahoney. Another shell came and burst into a tree, spraying shrapnel on all sides. The fragment that hit Jerry passed through the other man's shoulder. Jerry was killed instantly.'"

In 1947, the American Graves Registration Command discovered a soldier’s remains in the forest near Reipertswiller, France, but were unable to identify the soldier. The Unknown was buried at Ardennes American Cemetery in Belgium in 1949. 

In 2022, the Defense POW/MIA Accounting Agency exhumed the soldier’s remains and transferred them to a laboratory for DNA testing. This spring, they confirmed that the fallen soldier was Jeremiah Patrick Mahoney of Chicago, Illinois. He will be buried at Arlington National Cemetery in June of 2025.

This Veterans Day, Saint Ignatius College Prep is proud to commemorate the sacrifice of Jeremiah Mahoney and each member of our community who has given so much - in Private Mahoney’s case, everything – in the defense of this country.