I live next to one of these abandoned railroads, one of the earliest in the country actually, which Daniel Boone wrote about riding along with many U.S. Presidents as well as Kings and Queens of foreign countries. The items I have recovered from surface hunting and metal detecting this area have been eye opening from many aspects. The U.S. National Archives has the blueprints of the design for this railroad I live next to digitized and available online and many years ago I studied it out of curiosity for the value of understanding the history of my area. What I could not have known at that time of studying was that a few weeks later I would discover pieces from the construction that matched the U.S. National Archive designs to a T - I was stunned. I have also since come to learn these pieces are in great demand from avid railroad collectors but I just do it for the lulz and not the money. Through my 10 years of researching and exploring historical information in my area I would share with everyone that if you live near a historical location and have interest in the past do your research first.
As a serial entrepreneur my point for the HN community is that opportunity is everywhere and in studying history one can discover exactly where to look for such opportunity. This logic applies to nearly everything.