1830 if I recall correctly. It is mortarless construction. They were the first keystone arch bridges built in America. There were 10 in total build over the Westfield for the Albany to Boston rail line. This is the "B" bridge. It is 65 feet high. I Haven't been to the bottom of the "A" bridge yet. That one is 70' high. I was at the top of it. I just wasn't able to find a good path down to the river. The banks of this river are pretty steep on both sides in most places. One of the bridges was destroyed in a flood
The "E" bridge is a double arched bridge. I wasn't able to photograph that one because the sun comes up right behind it. I think these bridges are best photographed at sunset. Been going right around sun up (which means I am leaving at 4am, since it is a 2.5 hour drive for me). Will try to get out there in the afternoon sometime soon.
I drive through lots of old towns along the way, and I make mental notes of potential detecting sites as I drive. Still trying to figure out what I can detect in Northhampton (settled ~1654) and what I cannot.