The marriage actually took place in County Leitrim, but no surprise since all the action here is on the Cavan / Leitrim county border.
Patrick O'Hara married Margaret Kerrigan on 2 March 1868. Bachelor Patrick was as a farmer living in the townland of Sruhanagh (in the civil parish of Killinagh, County Cavan) here:
http://maps.osi.ie/publicviewer/#V2,600661,826666,9,7Spinster Margaret Kerrigan was an 18 year old farmer's daughter living in the townland of Derrinwillin (in the civil parish of Drumreilly, County Leitrim) which you can see if you pan a bit SW of Sruhanagh. Or this link will take you directly:
http://maps.osi.ie/publicviewer/#V2,598487,825312,9,7The marriage took place at Ballinagleragh RC Church in the townland of Drumnafinnila (also in the civil parish of Drumreilly, County Leitrim) which you can see if you pan a bit SSE of Derrinwillin. Or this link will take you directly:
http://maps.osi.ie/publicviewer/#V2,599577,823066,9,7Patrick's father was Charles O'Hara, a farmer, Margaret's father was Patrick Kerrigan, a farmer. The marriage witnesses were John Curnan and Catherine O'Hara. Griffith's Valuation shows a Charles O'Hara in Sruhanagh and several Keerekans in Derrywillin, local print date 1856-57.