While interned on HMS Maidstone, Keenan was the Commanding Officer of the Provisional IRA prisoners there.
[2] In March 1972, a month before his final release, he was paroled for the funeral of his son Colm, a Provisional IRA officer who had been shot by the British Army.
[9] Keenan was chairman of the Derry Citizens Defence Association between July and October 1969 and played a prominent role in the events surrounding the creation and defence of Free Derry, including the Battle of the Bogside.
[5] His wife Nancy Ward, who died in October 1970, was a member of Cumann na mBan who was interned in Armagh Gaol in the early 1940s.
[5][10] He is commemorated annually by Republican Sinn Féin in the month of March at the Seán Keenan Memorial (Celtic Cross) on Fahan Street in the Bogside area of Derry City.