Do you play Call of Cthulhu? Then you really ought to thank the New York Public Library for its generous donation to your nightmares.
If you're the Keeper of Arcane Lore in your Cthulhu-loving tabletop circle, you might want to thank the New York Public Library right about now. Or if you happen to run any kind of historic tabletop setting, or if you're designing a game set in the late Victorian period or earlier, or if you just like old stuff. You want to thank the NYPL because it's just released over 20,000 maps for anyone to download and use, free of charge, under creative commons.
"We've scanned them to enable their use in the broadest possible ways by the largest number of people," says the NYPL. It'd be nice if you credited the Library should you use its maps, as that helps the NYPL keep track of who's doing what with its images, but that's not a requirement. The idea is to inspire creativity, not tie everything up in red tape.
Don't think that, just because it's the New York Public Library, that all its images are going to be of the city and the state. Far from it; there's plenty here from all over the world, though naturally a lot of its collection will be New York images.