The Merrickville Blockhouse, completed in 1832 to accommodate some fifty men, was one of four blockhouses and about twelve other defensible buildings constructed along the Rideau Canal. The canal, built from 1826 to 1832 by Lieutenant-Colonel John By of the Royal Engineers, was intended as an alternative military supply route from Montreal to Kingston in the event of war. Although the blockhouse was never the scene of military action, it later served as lockmaster's quarters, a church, and a canal maintenance building. Its restoration was completed in 1965, and it remains one of the two blockhouses on the canal that have retained their original forms.