I don't know a lot about trains in particular, but mechanical technology was advancing very rapidly during this period. It's roughly when the mass production

I don't know a lot about trains in particular, but mechanical technology was advancing very rapidly during this period. It's roughly when the mass production of interchangeable machine parts started to take off. Singer (sewing machines) and Colt (revolvers) are two notable examples. https://en.wikipedia.org/wiki/American_system_of_manufacturing https://en.wikipedia.org/wiki/American_system_of_manufacturi...