The structure was modified in 1840 by the Canal Company at a cost of $40,000 concurrent with the construction of the Wrightsville Dam. Towpaths of different levels and with sidewalls were added to prevent horses from falling into river, as happened several times when the river flooded. The roof of the lower path formed the floor of upper path. In this way, canal boats were towed across the river from the Pennsylvania Canal on the Columbia side to the Susquehanna and Tidewater Canal at Wrightsville.