As the city of New York grew during the period after the Revolutionary War, large plots of land were sold and subdivided for the construction of brick-clad and brick-fronted houses. These Federal-style houses were built between the 1790s and 1830s, and they represent some of the oldest urban residential architecture in New York City. As the city continued to grow over the centuries, these small houses were often replaced with larger buildings, but some still remain.

Since its creation in 1965, the New York City Landmarks Preservation Commission (LPC)— the mayoral agency responsible for protecting and preserving New York City’s architecturally, historically, and culturally significant buildings and sites—has designated more than 36,000 buildings and sites, including many such Federal-style houses, both as individual landmarks and as part of historic districts. However, the LPC lacked a comprehensive analysis of how many Federal-style buildings had been designated across the city or where they were located—such information could only be gathered by culling through thousands of pages of reports. Now, with the completion of the LPC’s Historic Building Data Project, this information is easily accessible with just a few clicks.

In December 2017 the LPC consolidated decades of research by launching an enhanced version of its interactive web map, Discover New York City Landmarks, which includes detailed information about each of the nearly 34,000 historic buildings within the city’s 141 historic districts. The web map is based on the largest and most comprehensive historic building data collection created by any municipal preservation agency in the United States and is part of LPC chair Meenakshi Srinivasan’s initiative to increase efficiency and provide greater transparency and public access. The addition of building-by-building data complements the map’s existing information about the 1,405 individual, 120 interior, and 10 scenic landmarks and provides an unparalleled resource for understanding and exploring the city’s built heritage.

As part of the LPC’s designation process, the history and significance of each landmark and district is carefully documented in designation reports. These reports form the basis for the LPC’s regulatory work, and are frequently used by staff as well as property owners and applicants. Over the last 53 years, LPC staff have generated tens of thousands of pages of research with detailed building descriptions and histories. While the scanned versions have been available to the public since 2012, the documents were unwieldy, and users were not able to search for information across historic districts, which made it challenging to understand the full breadth of the city’s designated buildings.

The LPC tackled this issue with the help of The New York Community Trust, which provided funding for the Historic Building Data Project. The LPC hired four data fellows, who worked closely with staff to transfer building information from designation reports into a custom-built geospatial database. The LPC tapped into its own decade-long expertise in geographic information systems (GIS) to design the database structure and develop a technical process for data transfer.

The fellows entered information such as architect name, building style, and building type into the database, along with location information that can connect to the city’s extensive land-use and geographic data. Rules were established to ensure that the building information in the database accurately reflected the designation reports, which was particularly important because of the reports’ regulatory nature. Finally, LPC staff invested considerable time in quality control and data cleaning.

The public can now access all of this information on the Discover New York City Landmarks web map—an effective, accessible, and intuitive platform for data interaction and display. The map presents a pop-up for each landmark and building in historic districts, presenting information such as date of construction, architect, style, building type, and original use. The map also features powerful new tools to search and filter historic district building data by these characteristics. Filtering tools can, for example, easily identify and visually represent every apartment building in the Upper West Side Historic District or every Queen Anne–style row house in the Bedford Historic District.

The release of the new web map met the LPC’s goal of providing greater transparency and public access to agency research. In addition, the data have increased the agency’s own understanding of the designated buildings. With the data project now complete, it took only minutes how many Federal-style buildings have been designated across the city: 488, and they are clustered in the Greenwich Village and Brooklyn Heights neighborhoods.