The castle appears on a 1563 map of Leix and Offaly, marking its significance in the region during the Tudor period. Originally built and owned by the O’Lalor family, the castle changed hands in 1577 when Queen Elizabeth I granted it to John Piggott, part of the Crown’s broader strategy of displacing Irish Catholic landowners with English Protestant settlers.

The castle’s most dramatic chapter came during the Confederate Wars in 1646. Colonel Farrell and Colonel Roger McGuire’s regiments stormed Dysart, taking the castle by force and killing John Piggott in the assault. This violent episode was typical of the period, when Ireland was engulfed in conflict between Confederate Catholic forces, Royalists, and Parliamentary armies; with castles like Dysart serving as both strategic strongholds and symbols of political control.

Today, visitors to the site will find only modest remnants of this once formidable structure. The northeast angle tower still stands, constructed from limestone rubble that has weathered centuries of Irish seasons. This corner of the curtain wall is all that remains visible above ground, a lonely sentinel marking where the O’Lalors and Piggotts once held sway. Though the castle’s glory days are long past, these stones continue to tell their story of conquest, rebellion, and the endless struggles for control that characterised 16th and 17th century Ireland.