Cavanaugh's family emigrated from the tri-County region of southwest County Wicklow, on the Cos. Carlow and Wexford border.
In 1923, John Cavanaugh initially entered the automobile industry, working in the advertising department at Studebaker Corporation.
According to the New York Times, Cavanaugh's legacy at Notre Dame in the post-war years was "devoted to raising academic standards and reshaping the university administration to suit it to an enlarged educational mission and an expanded student body" and stressing "advanced studies and research" at a time when Notre Dame quadrupled in student census, undergraduate enrollment increased by more than half, and graduate student enrollment grew fivefold.
Cavanaugh reorganized the administration in order to free himself to pursue fundraising activities and to act as a salesman for the University.
Cavanaugh's reorganization created five vice presidents, who focused their attention on the various aspects of the rapidly growing University.
During his many years of association with Joseph P. Kennedy, Father John was called on for advice and assistance in times of difficulty.
[5] Joseph P. Kennedy sparked up a friendship with Father Cavanaugh when he became a member of University of Notre Dame's Board of Trustees.
Beginning in 1958, Father Cavanaugh advised Joseph P. Kennedy on a strategy for addressing American Protestant concerns about the potential election of a Roman Catholic president.
[7] The future Senator from the State of Pennsylvania was a civil rights attorney then teaching at Notre Dame Law School.
Cavanaugh was present with the Kennedy family at Hyannisport in 1960, as they anxiously awaited returns from the swing states of Michigan, Illinois, Minnesota and California in the unexpectedly close Presidential election.