Online sources for historical property research

For NYC, New Jersey and Connecticut Sanborn Maps, 1867-1970.
Access to large-scale historical maps for towns and cities in New York, New Jersey and Connecticut. (Proquest.) Sanborn fire insurance maps are valuable historical tools for urban specialists, architects, geographers, planners, environmentalists and anyone who wants to learn about the history, growth, and development of American cities, towns, and neighborhoods. (Accessible onsite at SIBL and in the Map Division, Humanities and Social Sciences Library)

Photographic views of New York City

NYPL Digital Gallery. More than 54,000 New York City archival photographs (and their captioned versos) from the 1870s-1970s arranged by borough and street; the majority are exterior building views and neighborhood scenes from the 1910s-1940s.

Also see: Researching an Architectural Structure, a library research guide by the New York Public Library’s Art & Architecture Collection.