Fourmilehouse is a village or population centre within the townland of Ballinderry. A townland is the smallest division of land in Ireland, and would in turn be part of a civil parish, which would be part of a county.
Townlands are often not shown on modern maps but will be included on the 1st edition OSI maps - see
Four Mile House, Co. Roscommon (click on the historic or historic bw option to see the old maps) Four Mile House is not specifically marked on the old map. I dont see a townland of Ballinderry in the area at the moment but will have a closer look later on.
Details for Ballinderry are listed on the townland database at :
www.thecore.com/seanruad Townland: Ballinderry
Barony : Ballintober South
Civil Parish : Kilbride
Shane