The Clan MacMahon is descended from The Three Collas, brothers who were nephews to the High King of Ireland. As the story is told, these three were daring and ruthless and attempted to take all of Ireland in 322 AD. They ended up ruling a portion of the island consisting of Counties Monaghan, Armagh, and parts of Fermanagh, Louth, and Tyrone. Their descendents were to rule this part of Ireland for some 1300 years, this Kingdom of Airghialla, later known as Oriel. The MacMahon branch descended from a fellow known as Mathghamhain, who was slain in 1022.

The first Mac Mahon to hold the title 'King of Airgialla', according to the Annals of the Four Masters, was Eochaidh Mac Mahon who became King in 1250 and was killed in 1273. The MacMahons continued to rule Oriel for some 400 years. These were tumultuous times and change was in the wind. Ireland consisted of perhaps 300 small kingdoms. Powerful families on all sides were constantly seeking to expand their lands. Gaelic rule was coming to an end. The Normans were gaining in power....but I am getting ahead of myself. There is a story to be told in these pages. Let us begin at the beginning and end at the end. Join us as we brush away the overgrowth and peer into the past....