Narrows Lockstation looking towards Big Rideau Lake photo by: Ken Watson
Prior to the construction of the canal, the Upper or Little Rideau and the Lower or Big Rideau Lake were one body of water. At the Narrows, a tongue of land extended from the north side to within 100 feet of the opposite shore. To lessen the amount of excavation into hard granite required at the Isthmus (Newboro), Col. By and his engineers decided to build an earth and clay dam at the Narrows to raise the water level 4 feet 10 inches (about 1.5 m.), thus creating the Upper Rideau. A weir and a lock linked the two Rideaus. A blockhouse was built in 1832-33 to defend this strategic site. Over time the dam was widened and in 1867 a bridge was added to link the north and south shores by road.