The Gaelic kingdom - of Oirgialla (Oriel) played an important part in the history of the North of Ireland for nearly a thousand years until destroyed in the 16th and 17th centuries by England under Queen Elizabeth, Cromwell, and King William of Orange. Monaghan was part of Oirgialla. Early rulers in the area included the O'Sherry's and the O'Carroll's who were dominant by the 11th century. By the 13th century the McMahon's were in control of the area we now know as Monaghan. They retained control until the early 17th century when they and the rebel O’Neill’s, Maguires, O’Donnell’s were defeated.

Monaghan county has existed since 1585, when the Mac Mathghamhna(Mac Mahon) rulers of Airgíalla/Oriel agreed to join the Kingdom of Ireland.

In 1591 the MacMahons leaders entered a settlement with the English. As a result, Monaghan was not included in the scheme for the Plantation of Ulster. This relationship with the English came to…