
The settlers of this region were largely Scotch-Irish, a kind of overflow of the migration of these nationalities into the Cumberland Valley which began in 1735. At that time, it included the present day townships of Carroll and Franklin and the Boroughs of Dillsburg and Franklintown. The Township was "laid out" or incorporated in 1745. Not only is Monaghan one of the oldest municipalities in York County, several other communities were once part of Monaghan Township.

Monaghan Township celebrated its 250th anniversary as a Township in 1995.
