NYC Rapid Transit in Maps, 1845-1921: The Street Railroads of New York and Vicinity
​
​https://www.nypl.org/blog/2015/04/03/nyc-transit-maps-1845-1921

Photos of NYC in the 1860s

https://seeoldnyc.com/tag/1860s/

History of the NY & Harlem Railroad

https://www.harlemworldmagazine.com/the-harlem-line-from-ny-and-harlem-railroad-was-the-first-streetcar-company-in-the-world/