The picture above includes the top of one of Lockport’s modern lock gates. The railroad bridge you see crossing the canal in the distance doesn’t look like most other bridges. Trains cross this bridge on the very top, and the trusswork that gives the bridge strength between supports is beneath the tracks, rather than above. This makes the bridge appear to have been built upside-down.
Tour guides at the site like to explain the unusual bridge by saying that because railroads were in competition with the canal for freight cargo business, they used the hanging bridge trusswork as a way to limit the size of ships that could navigate on the canal. No doubt it’s fun tell people that clever story, but if you visit Lockport and hear this on one of the tours, don’t believe it. The real reason is far less interesting: Bridge truss-work is built above the load it’s intended to carry – in this case the railroad – only when there’s not enough room underneath, which is usually the case. Building it above means that the bridge has to be wider to accomodate both the traffic AND the truss-work. That means more steel and higher building costs. Here the ground on both sides was high enough to allow the railroad to save some money by building a narrower bridge with the truss-work below the tracks, with plenty of room to spare for canal boats to pass underneath. It was about saving money: Nothing more.
In case you’re still not convinced, consider the highway bridges you see in the distance in this shot taken from the top of the “upside down” bridge. The railroad engineers had no reason to be concerned about tall ships getting under their bridge. They knew very well that the waterway was already crossed by hundreds of bridges like these that were a lot lower than the one they were planning.
While we’re here, it’s fun to compare old pictures with modern scenes. Notice in this print that there’s a railroad bridge at about the same spot already. We think the date is about 1839, but it’s good to remember that paintings aren’t photographs, and that artist details are often more entertaining than reliable. This image with all its bright red roofs and whimsical architecture (the shack on the left) probably bear that out.