This family, descended from Donnchad Mac Niocal Og, built their castle here but lost control of it during the turbulent late 16th century. By 1596, Melaghlin McKeogh had surrendered the castle to Irish rebels, and following his death in 1604, the property was sold to Thomas Dillon of Curraghboy. The Dillon family would maintain their presence here for decades; Richard Dillon held over 400 acres at Castlesampson in 1640 and managed to retain his lands through the upheavals of the 1660s.

Today, visitors can trace the footprint of the rectangular castle structure, which originally measured about 13.2 metres east to west and 10 metres north to south. The south wall remains the most impressive survivor, rising to five metres in places and showing clear evidence of its defensive base batter and the springing points of an east to west barrel vault that once supported an upper floor. The southeast corner juts outward, likely the location of a garderobe, whilst dressed stones from the original structure have found their way into nearby field walls over the centuries.

Archaeological investigations have revealed that Castlesampson was more than just a standalone tower house. Stone spreads to the south mark the remains of a bawn, a defensive courtyard measuring roughly 18 by 12 metres that would have protected livestock and provided additional security. Remote sensing surveys conducted in 2014 unveiled a complex palimpsest of features beneath the surface, including what might be an enclosing fosse or defensive ditch, suggesting the site evolved considerably over its active lifetime. Despite extensive testing about 80 metres west of the castle in 2006, no additional medieval material was recovered, leaving some questions about the full extent of the settlement unanswered.