The Department of Marine published the following description of Île du Moine Range in 1906:
The front lighthouse stands on the west end of Ile du Moine, about 400 feet back from the water's edge. It is a square wooden building, painted white, surmounted by a square wooden lantern painted white with a red roof. The building is 21 feet high from its base to the top of the ventilator on the lantern, and stands on a concrete pier 26 feet high, square in plan, with battered sides, whitewashed. The light shown is a fixed white catoptric light, elevated 43 feet above the summer level of the river, and visible five miles in the line of range. The back tower stands 1,590 feet from the front one. It consists of an open steel framework, square in plan, with sloping sides, painted brown, surmounted by an inclosed wooden watchroom and an octagonal iron lantern. The side of the framework facing the channel is rendered more conspicuous as a day beacon by being covered half way down with wooden slatwork. The lantern roof is painted red, the lantern sides, the watchroom and the slats are painted white. The height of the tower from its base to the top of the ventilator on the lantern is 86 feet. The tower stands on a whitewashed concrete pier 19 feet high, square in plan, with battered sides. The light shown is a fixed white catoptric light, elevated 108 feet above the summer level of the river, and visible five miles in the line of range.Etienne Provencal was hired as the first keeper of the front light at an annual salary of $125, while Paul Mongeau was paid an annual salary of $100 as the first keeper of the rear light.
The work was performed by day labour under the Montreal agency; the steel tower was supplied by the government shipyard at Sorel, and the total cost of this work, inclusive of the tower, was $17,022.13.
At some point between 1955 and 1994, the rear tower was replaced by the current fifty-seven-foot-tall, square, skeletal tower that displays a light at a focal plane of ninety feet above the river. During this same period, the characteristic of the range lights was changed from fixed white to fixed green.