The New York Public Library’s new NYC Space/Time Directory is imagined as a “digital time-travel service,” a two-year project engaging the library’s collections of maps and geospatial data through interactive tools. The first such tool, Maps by Decade, was launched this month, plotting 5,000 digitized New York City street maps across the five boroughs, organized by decade from 1850 to 1950.

“The goal of the Space/Time project is to connect the library’s collections through space and time,” Bert Spaan, NYPL’s Space/Time Directory engineer, told Hyperallergic. “I’m using many of the projects the library has used in the past.” For instance, Maps by Decade expands on the thousands of data sets, outlines, and locations crowdsourced and georectified through the seven-year-old Map Warper, combined with digitizations from the map collections. Future tools may employ the crowdsourced data of What’s on the Menu?, focused on the transcription of historical restaurant menus, or Building Inspector, where users identify buildings shapes and other details on old insurance atlases.

Navigating a modern map of the city, users can activate 19th-century plans of Central Park, or early 1900s atlases of the Brooklyn shore, visualizing them against the current grid. Maps of towns now absorbed into the city, like Flatbush and Gravesend, can be situated in their contemporary neighborhoods. This makes the map collections much easier for researchers to navigate, and instantly accesses a century of street-level development data.

“There’s one page, one website, where they can go and see all the data we have,” Spaan added. Furthermore, each map is linked to its geospatial data set, so anyone can use this resource for their own cartographic projects. “The way we’re doing this, having all the software in the open, that is something that I have not seen before, and is really important for those researchers,” Spaan said. “They can use it in whatever way they like.” All the source code for the project is additionally available on GitHub.

Spaan noted in a NYPL blog post that the Space/Time Directory aims to be “like Google Maps, but with a time slider.” In the coming months, he hopes to introduce tools that facilitate searching for addresses on defunct streets, and access to historical photographs from the OldNYC tool, continuing to stitch together disparate physical and digital data at NYPL. For Maps by Decade, there could be a way for users to fill in visible voids of content. Since November, he’s also been hosting a series of historical data and maps meet-ups, where the public can get involved and collaborate with historians, developers, and librarians.

“All these tools help us to learn something about some aspect of New York City history, and the new project aims to bring all these things together, to give the people one place where they can find historical maps and photographs, and see how the streets looked in the past,” Spaan said.

Maps by Decade is accessible online through the NYC Space/Time Directory.