Callahan graduated from Illinois College in 1955 with a B.A. in English, which he later applied to a career that incorporated his passion for writing and journalism, beginning as a reporter at the State Journal-Register in Springfield and taking assignments for the New York Times and Time Magazine. He went on to find his place in politics, serving as deputy press secretary under Illinois Governor Samuel Shapiro, later Governor Otto Kerner, and eventually serving as chief of staff to Lt. Governor Paul Simon and U.S. Senator Alan Dixon. He returned to his love for baseball when he finally ended his career as the first director of government relations for Major League Baseball until 1998. Callahan was a strong supporter of athletics at the College and helped to transform athletics at the College through his consistent generosity.

The Callahan family legacy at Illinois College includes Gene’s wife, Ann Hammond Callahan '55, who he met at Illinois College, his daughter Congresswoman Cheri Callahan Bustos '83 and her son Nick Bustos ’10. Cheri shares her father’s love for sports and politics. The Illinois Congresswoman was inducted into the Illinois College Sports Hall of Fame in 1994 for her accomplishments in basketball and volleyball.