The ward was a Labour stronghold as the party successfully held the seat at every election. David Sneller was the only councillor elected as he represented the ward from 1984 to 1999.
The Cumnock South and Old Cumnock ward was created for the 1984 local elections by the Initial Statutory Reviews of Electoral Arrangements in 1981 from the former Cumnock Burgh and Old Cumnock Parish wards. The ward took in the southern part of Cumnock including Netherthird as well as Skares.[1] Minor changes were made to the ward's boundaries in Cumnock town centre following the Second Statutory Reviews of Electoral Arrangements in 1994.[2] After the implementation of the Local Government etc. (Scotland) Act 1994, the boundaries proposed by the second review became the Formation Electoral Arrangements for the newly created East Ayrshire Council – an amalgamation of Cumnock and Doon Valley District Council and Kilmarnock and Loudoun District Council. In 1998, the ward was abolished by the Third Statutory Reviews of Electoral Arrangements. The majority of the area represented by the ward was placed into the new Ochiltree, Skares, Netherthird and Craigens ward. The remainder of the ward was split between the Auchinleck, Cumnock East and Cumnock West wards.[3]