John D. Killian was born in Woodhaven, New York, on November 5, 1928. He was educated in Long Island public schools, at Hofstra University (A.B. 1950) and Cornell Law School (LL.B. 1953 and LL.M 1954). He served in the U.S. Army Counterintelligence Corps from 1955 to 1957. From 1957 to 1964 he served as Deputy Attorney General of Pennsylvania, principally assigned as Chief Counsel to three Departments: Public Instructions, Public Welfare, and Health. He tried and argued dozens of cases before state and federal courts, including the United States Supreme Court where he argued the famous "Bible-reading" case.
In 1964, he entered private practice and served as General Counsel to the Pennsylvania Higher Education Assistance Agency from 1965 to 1992, as Legal Counsel to the Pennsylvania Health Care Cost Containment Counsel from 1988 to 2002, and as General Counsel to Presbyterian Homes from 1964 to 2001. He attracted a large clientele of individuals and corporations and founded the firm of Killian & Gephart in 1967. He became of Counsel to the firm in 2001 and continues practicing law, specializing in trusts and estates.
John was a member and Chairman of the Public School Employee's Retirement Board from 1971 to 1980, served as a member of the Governor's Study Commission on Public Employee Relations from 1976 to 1978, and served as Chair of the Pennsylvania community Service Advisory Board (PENNSERVE) from 1996 to 2000.
John was a Trustee of the Dauphin County Library System from 1972 to 2008, served as a Director of the Pennsylvania Chamber of Business and Industry, served as Chair of Leadership Pennsylvania and the Pennsylvania College of Art & Design, was Co-Founder and served as a Director of the Pennsylvania Center for Excellence in Education which oversaw the Governor's Schools. He also served as a Trustee of Lancaster Theological Seminary, as a Director of the Council for Public Education, and on various church and charitable organization boards. In 2006 he was named Volunteer Fundraiser of the Year by the Association of Fundraising Professionals.