The bridge you see in the picture above is like many others that crossed the Erie Canal during the latter half of the nineteenth century, but this particular bridge was used for an unusual purpose. This bridge – which was moved from it’s original location to this park in Palmyra – was a change bridge. It’s purpose was to transfer mule teams and their drivers from one side of the canal to the other when the towpath had to change sides for some reason. In the picture above, imagine the canal passing under the bridge, with the towpath coming toward you on the left from the distance, and proceeding in the same direction on the other side of the canal on the right. You should be able to trace the route of the team up the bridge on the left side, then back down the ramp toward you on the right, with the tow-rope attached to the animals all the while, and the boat coasting on the water waiting to be towed again once the animals with their driver are on the other side.
This is the sign at the change bridge pictured above. The text on the sign reads:
Squire Whipple, the man who invented the Aldrich Chain Bridge in 1858, was correct. Writing about the benefits of using iron rather than wood in bridge construction, Whipple said that, “The iron bridge gives fair promise of enduring for ages”. By applying his mathematical training, Whipple added science to the art of bridge building. The formulas that he developed and published carefully calculated the stress that iron could endure. The bow-string trusses that he patented and used in his bridges proved their strength as well as their beauty. Dozens, if not hundreds of these bow-string truss bridges once crossed the Erie Canal. The 74-foot by 14-foot cast and wrought iron bridge here in Aqueduct Park is Whipple’s oldest known surviving structure and one of the oldest iron truss bridges in the country.