The following description of Gentilly Range was published in 1907:
The front lighthouse is a square wooden building, painted white, surmounted by a square wooden lantern painted white with the roof red. The building is 23 feet high from its base to the top of the ventilator on the lantern. The fixed white light, elevated 45 feet above the summer level of the river, is visible seven miles in the line of range. The illuminating apparatus is dioptric of the fourth order, and the illuminant petroleum vapour burned under an incandescent mantle. The back tower is erected one and a third miles from the front one. It consists of an open steel framework tower square in plan, with sloping side, surmounted by an inclosed wooden watchroom and an octagonal iron lantern. The upper part of the side of the framework facing the channel is covered with wooden slatwork. The lantern roof is painted red, the remainder of the lantern, the watchroom, and the slats, are painted white, and the steel frame brown. The height of the tower from its base to the top of the ventilator on the lantern is 81 feet. The fixed white light, elevated 101 feet above the summer level of the river is visible eight miles in the line of range. The illuminating apparatus is dioptric of the fourth order, and the illuminant petroleum vapour, burned under an incandescent mantle. The steel tower was supplied by the Goold, Shapley, & Muir Company, of Brantford, Ontario, for $668.50, and the cost of erecting it and completing the piers, which were practically finished during the preceding year, was $1,454.40.
Adolphe Lebleu was hired as the first keeper of the front light at annual salary of $250, while Delphis Mailhot earned $150 a year for looking after the rear light. In 1916, a fire broke out in the lantern room of the back range light, necessitating the installation of a new cast-iron lantern room and a thirty-inch reflector to replace the lighting apparatus destroyed in the fire.
A new concrete pier surmounted by a concrete lighthouse was erected on the flats in 1920 to replace the original pier and lighthouse that were moved out of position by ice shoves. The current rear range tower was erected around 2010.