There may be no device more important to the American economy than the automatic railroad coupler. This device holds together the trains that keep the economy moving better than any other mode of transport. Automobiles, coal, oil, Boeing fuselages, grain, passengers, windmills, and more are pulled daily by trains criss-crossing the continent. Everyone of those trains are linked together with the descendent of the "Janney Coupler", and are all interchangeable...
This was shot on Southeastern Pennsylvania's Strasburg Railroad from the "Hello Dolly" car.
This photo is avaliable for sale at http://www.bigdiehlphoto.com
under "Railroads" and then "East Coast Railroads"