West Glamorgan was created on 1 April 1974, by the Local Government Act 1972 from the county borough of Swansea, the municipal boroughs of Neath and Port Talbot, the urban districts of Glyncorrwg and Llwchwr, Gower Rural District, Pontardawe Rural District, and all of Neath Rural District except the parish of Rhigos. From 1982, the main council offices were located in County Hall, Swansea.
West Glamorgan had four districts, as follows:
Following the Local Government (Wales) Act 1994, West Glamorgan and its component districts were abolished on 1 April 1996, the area being divided into the two unitary authorities of Swansea and Neath and Port Talbot. Lliw Valley was partitioned between the two authorities. A West Glamorgan preserved county was created for the limited functions of Lieutenancy and High Shrievalty.
The first three maps are provided by A Vision of Britain through Time
These maps were found on Wikimedia Commons
These maps of Glamorgan post-1974 were found on another site and are very useful for sorting out the up-to-date geography of the area