In the 1830s, a rail line linked Elkton, Maryland, with New Castle, Delaware, shortening the time it took to shuttle people and goods between the Delaware River and Chesapeake Bay. Today you’d never know it had been there. A photograph snapped years after the line had been abandoned captures a stone culvert halfway to collapse into the creek it spanned. Another image, captured even later, shows a relict trail that looks more like a footpath than a railroad right-of-way. The compacted dirt seems wide enough to accommodate no more than…