McKennan entered politics as a Democrat, and was Assistant Corporation Counsel of Utica; Counsel to the Municipal Water Works of Utica. In 1948, he was elected to the New York State Senate (41st D.) and served one term in then 1949 and 1950. At only age 29, this made McKennan the youngest person elected to the New York State Senate until the election of David Carlucci in 2010.[2]
On May 7, 1955, he married Marguerite Gallagher, and they had three sons.
McKennan was Mayor of Utica from 1956 to 1959.[3] As mayor, McKennan was best known for spearheading the construction of the Utica Memorial Auditorium (now known as the Adirondack Bank Center) and securing the funding from Governor W. Averell Harriman for the North-South Arterial Highway. His other accomplishments included the construction of Valley View Golf Club and the first public swimming pool located in North Utica.[3] A wide-ranging corruption scandal resulted in the indictment of numerous Utica city employees during his term, but he himself was not indicted.[4] He did not run for reelection in 1959, instead running for City Judge of Utica, but was defeated by Matthew S. Ogonowski Sr.[5]
In March 1982, Governor Hugh Carey appointed McKennan to the New York Supreme Court (5th D.) to fill the vacancy caused by the appointment of Richard J. Cardamone to the U.S. Court of Appeals for the Second Circuit.[6] In November 1982, McKennan ran for a full term, but was defeated, and left the bench at the end of the year.
In 1988, McKennan was appointed as a Judicial Hearing Officer by the Chief Administrative Judge of the State. The Board of Regents of the University of the State of New York appointed him to its review board for licensed professionals. In 1999, he was appointed as a Judicial Hearing Officer for the State Retirement System.[3]
