Gwent County Council provided county-level services to the new borough.

[2][3] The district's name (meaning "below the grove") was derived from the ancient parish of Mynyddislwyn which covered its area.

This was shown in the borough's coat of arms which represented a mountain below a grove of oak trees.

The first election to the council was held in 1973, initially operating as a shadow authority before coming into its powers on 1 April 1974.

The building subsequently served as offices for Caerphilly County Borough Council until 2015 and has since been demolished.