A Democrat, he served in the Montana Senate from 1967 to 1974 and was president pro tempore in 1974.
Keenan was born in Butte and was educated in local schools of the Anaconda area.
[1] Of Irish descent, he was married to Ann and with her had five children, including Nancy Keenan.
[3] In the State Senate, Keenan served on the Legislative Council as well as on the Journal committee and Local Government subcommittee as chairman.
[4] In 1975, Keenan was named chairman of the Deer Lodge County Democratic Central Committee.