File:Paulinskill Viaduct - April 26, 1911.jpg

Summary
The Delaware, Lackawanna & Western Railroad used this image for promotional purposes over the years. None of those publications would have been copyrighted either.
 * Other information:

Licensing
The Delaware, Lackawanna & Western Railroad never copyrighted any of it works according to its last president, Perry M. Shoemaker (1953-1960), who was interviewed in 1992. Shoemaker died in 1999.