The New York Public Library has made available a HUGE collection of scanned photographs, documents, menus, stereographs and post cards.
http://publicdomain.nypl.org/pd-visualization/
I hope you have a fast internet connection... you'll need it!
Just search whatever interests you and see what comes up.
Here's a few gems:
How about a rare view of a two-dome tank car?
That last photo is part of the base for the Unisphere for the 1964 World's Fair!
Enjoy!
Ed
I've been using the New York Public Library for some time now while researching the various New York harbor float yards. Be sure and search by streets and cross-streets around where you are interested. There is a lot of "railroad" background. Some of the best photos of the Bronx's Harlem Transfer are from street views across the Harlem River in Manhattan. The quality of the photos is amazing. You can zoom into a small background scene and still see extreme detail.
Ray
Thanks, Ray! Pretty cool stuff