The Princeton University Library has digitized a number of posters from the Interborough Rapid Transit Subway Company. The posters, designed by the public relations firm Ivy Lee, were displayed in subway cars to provide information to riders about changes in fares and routes, safety issues, and other matters of interest. The collection consists of 385 images dating from 1918 to 1932; many of them provide financial information about rates, company dividends, and a general look at an early rapid transit system.
October 29, update: Jonathan Rees over at "More or Less Bunk" was moved by this post to go off in search of a better site, and found the massive collection of the London Transport Museum, which displays over 5,000 items in a searchable collection.
October 29, update: Jonathan Rees over at "More or Less Bunk" was moved by this post to go off in search of a better site, and found the massive collection of the London Transport Museum, which displays over 5,000 items in a searchable collection.