Cartophiles rejoice — the NYPL recently made over 20,000 historical maps from its database free to access, download, and use. The library's Lionel Pincus & Princess Firyal Map Division created an entire website called Map Warper where users can create an account and access all the maps, which are available courtesy of Creative Commons. Many of the maps detail New York City from 1852 to 1922, but there are also unlikely collections from the mid-Atlantic United States and the Austro-Hungarian empire. The library also created a tool that lets you overlay the maps on existing images from tools like Google Earth, so if you've ever wanted to compare topographic details from different generations, now's your chance. Read more about the 15-year long process of organizing and scanning the maps at NYPL.