The New York Public Library is home to one of the world’s premier map collections, including more than 433,000 sheet maps, and 20,000 books and atlases, published between the 15th and 21st centuries. More than 20,000 of these items have been digitized and are available through the Library’s Digital Collections portal and the Map Warper tool.

Map Warper

The Map Warper is a free online tool that enables you to align digital images of historical maps with their present-day locations through a process called georectification, or "warping: maps. This tool is for everyone: librarians, students, teachers, map lovers, history buffs, artists, and researchers.

Maps that have been rectified can be found through the Map Warper’s geosearch function, which allows you to search for maps by geographic location. From the Map Warper’s homepage, you can use the Find Maps by Location tab to search for individual maps, or the Find Layers by Location tab to search for collections of maps or atlases.

Finding Maps by Location

The Find Map by Location tab allows you to search for rectified maps, and the page is split into two halves: On the left is a list of historical maps, on the right is a present-day map. As you move around the map, the Found Maps list on the left updates to show historical maps available on the Map Warper that correspond to whichever location you are viewing on the present-day map on the right.

(Tip: Using the pink time slider above the Found Maps list narrows your results to maps whose dates are within the specified time frame.)

Selecting a map from the Found Maps list highlights the selection and its geographic boundaries (or extent) on the present-day map. This is a quick way to decide if the map you’ve selected covers your area of interest.

Then, to view the selected map, click Open Map under the map’s title and year on the Found Maps list, or click Open Map in New Page in the dialog window on the present-day map. The Find Layers by Location tab similarly allows you to search for entire collections of maps at once. You can open the atlas by clicking Open Layer or Open Layer in New Page.

The map or atlas you select will open in a new tab on your browser, allowing you to go back to your search and select other maps or refine your search. You will now be able to view or download the rectified historical map or atlas using the Show, Preview, and Export tabs. You can even view and help with a map’s rectification in the Rectify tab.

The Map Warper provides new ways for scholars, students, and enthusiasts like you to explore history across time periods, and add your own knowledge and expertise by transforming digital images of historical maps into the tiles of a virtual atlas. With the ability to search more than 11,000 digitized and rectified historical map images, the question is not "What are you looking for?", but rather "What will you find?"