This is one of four blockhouses which, with some twelve other "defensible buildings", were constructed along the Rideau Canal. The canal, built 1826-32 by Lieutenant-Colonel John By, Royal Engineers, was designed to serve as an alternative military supply route from Montreal to Kingston in the event of war. The Merrickville blockhouse was completed in 1832 to accommodate some fifty men. It was never the scene of military action, but has served as lockmaster's quarters, a church and a canal maintenance building. Restoration of this fine example of early military architecture was completed in 1965, and it is one of the two remaining blockhouses on the canal which have retained their original forms.