Mac Coghlan castle was constructed around 1500 AD, earning a mention in the Annals of the Four Masters when it was recorded in 1520. The castle belonged to the Mac Coghlan family, who held considerable power in this region during the late medieval period. Historical accounts from researchers like Cooke in 1875 and O'Flanagan in 1933 have helped piece together the castle's story, even though the physical structure has long since disappeared from the landscape.

Archaeological investigations have attempted to uncover traces of this lost fortress. In August 2007, archaeologist Anne Carey conducted trial trenching at the site where an agricultural building was planned. Four trenches were carefully excavated across the area, but the dig yielded no artefacts or features that could be definitively linked to the castle's medieval past. This isn't entirely surprising; many Irish tower houses and castles from this period have left minimal archaeological footprints, particularly when stone was robbed for later building projects or the structures simply deteriorated over centuries.

Despite its invisibility at ground level, the site remains significant for understanding the political landscape of 16th century Offaly. The Mac Coghlans were one of several Gaelic families vying for control in the Irish midlands during a turbulent period that saw increasing English influence and the gradual erosion of traditional Gaelic power structures. The castle would have served as both a defensive stronghold and a symbol of the family's authority, standing as a testament to their influence until it eventually fell into ruin and memory.