Sir William Petty established a settlement/plantation scheme here ("Kilmare") around 1670 comprised of English, Cornish, and Welsh protestants. It wasn't however until around 1775 when the 1st Marquess of Lansdowne (William Petty-Fitzmaurice) took an interest in the settlement that the town took on its present shape.

He directed that the town's two streets (Henry Street and William Street) be designed to cross each other at an angle thus creating an " X shape " street plan complete with a triangular marketplace. It is thus one of Ireland's first "planned towns".

The influence of the "Marquess of Lansdowne " can be still seen today in the names of some of the local buildings (Lansdowne Arms hotel, once the town residence for William Petty – Fitzmaurice) to the title deeds of many of the lands in and around the Kenmare area which still bear references to the Marquess of Lansdowne.