St Mary's GAC Slaughtmanus was founded in 1978 when two local teams, Wolf Tone Slaughtmanus, founded in 1958, and St Mary's Mullabouy, founded in 1976, amalgamated. On 30 November 1978 Slaughtmanus secretary Edmund Brewster received a letter from the secretary of St Mary's GAC Mullabouy requesting the possibility of the two clubs amalgamating. The two clubs decided to have a public meeting on 20 December 1978. The meeting was chaired by An tAth. Seán Ó Gallchobhair (the curate in Tamnaherin end of the Parish at the time). After much discussion the two clubs decided that the best thing for the future of the GAA in the area was to amalgamate. The new club was to be called St Mary's GAC Slaughtmanus. The club colours were to be Red and Black. These colours had no significance to either club. The newly formed committee approached The Doire County Board to ask if the senior and reserve teams could play in The All County Division 2 as Drumsurn did not want to be promoted that year to 1st Division. The County Board agreed and St Mary's GAC Slaughtmanus played its first match against Glenullin in March 1979. In 2000 it was decided to change the club colours to green and red, green representing the old Slaughtmanus and red representing Mullabouy. Playing numbers have increased since
Strathfoyle team Enagh became defunct. The club had a new pitch installed and pending a lottery grant plan further developments such as a training pitch and a new hall. ==Honours==