Thomas Delahanty, the son of Irish immigrant parents, attended Lewiston High School and excelled in baseball and football. He worked in local textile mills to fund his law school education, earning a law degree from the Columbus School of Law after an athletic scholarship to George Washington University. Despite missing military service in WWII due to an ulcer, he became a special agent for the FBI. Upon returning to Lewiston, Maine, he opened a law office and later transitioned into public service, holding various judicial positions, including appointments to the Maine Superior Court and the Maine Supreme Judicial Court.