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House History Research at The New York Public Library: PREPARATION

A Guide For Researching the Histories of NYC Residential Buildings


To start researching the history of a building in New York City, it's helpful to have 3 pieces of information about it.

  1. The Borough Block and Lot number, sometimes just called the Block and Lot number. This is the nearest you'll get to a permanent alpha numeric identifier, because in New York City street names and building numbers change all the time. 
  2. The NB, or New Building number: this will help you search for paperwork associated with the construction (or major alteration) of a building.
  3. Geographic location. Borough Block and Lot numbers don't appear until the 19th century. So it helps to get a sense of where in the landscape, and in relation to other cultural features, a building is, so that we can develop a history of the lot it is built upon. The Northwest corner of 6th Avenue and Waverley Place, for instance. Maps will help us locate this information, as well as written descriptions in property deeds and newspapers.

Often this information may be found online, in databases, and digitized property maps.



Department of Buildings Building Information System: The NYC Department of Buildings address searchable database Building Information System (BIS) is where you should begin your building research. Searching by current address, you can pull up your building's Property Profile Overview, that includes:

  • Block and Lot number. The Block and Lot number is vital to your research, the number that best identifies property through shifting geographical and electoral boundaries, and changing street names and numbers.
  • New Building (NB) number (the number associated with the original application for its construction): it is located under Actions. Make note of these numbers - if available - as you will need them during the course of your research.
  • Information regarding  cross streets, and landmark status.
  • Other digitized documents, including certificates of occupancy, complaints, inspections etc.


NYCityMap: An alternative starting point is the NYCityMap portal, a digital information hub in the form of a map, that also links to BIS. Here you will find information pertaining to current building ownership, basic building history details, the building's Block & Lot number, and a wealth of information pertaining to the building's structure, and to the community it is located in. This database covers the five boroughs of New York City. NB, the date of the building's construction listed in both BIS and NYCityMap, may be an estimate: the entry might say 1920, but your building could be older. 


Historical fire insurance maps will describe a building's location, construction materials, and use over a period of time, as well as the names of some businesses, factories, churches, and the boundaries of former farmland — useful if you're going right back in time. Visit The New York Public Library's Map Division to look at these and other maps, or consult them digitally, via the Map Division's collections of Fire Insurance, Topographic, Zoning, and Property Maps of New York City. In addition to NYPL's collections, Queens LibraryBrooklyn Public Library's Center for Brooklyn History, and the New-York Historical Society all have extensive map collections that describe the built environment in New York City.

Often included in fire insurance maps is a building's historical 

  • block and lot number
  • building number and street name
  • dimensions
  • measurable distance from other landmarks
  • a key, usually on the first page of the atlas, that explains the meanings markings and color codes on the maps, e.g. Pink = brick

For fire insurance maps outside of NYC, see the Library of Congress map collections online, below.

More about maps...

Navigating Research at the Map Division research guide, for more information on how to search for maps at NYPL.

Using Maps for Genealogy Research - includes detailed description of the history and uses of fire insurance maps since they were first published, in New York City in the 1850s, as well descriptions of historical auction maps, cadastral maps, and topographical maps, all invaluable sources of information when conducting building research.

Walking with your ancestors: A Genealogist's Guide to Using Maps and Geography by Melinda Kashuba (2005)

Using Maps in Genealogy / United States Geological Survey

Sanborn Maps / Library of Congress 

Digital Sanborn Maps, 1867–1970 Requires NYPL library card.

Above: Example of Sanborn map key. Courtesy of the Library of Congress Geography and Map Division.


Above: The NYC Department of Buildings Buildings Information System Property Profile Overview for 385 Avenue of the Americas, aka The Waverly Diner. Accessed 2020. Included in the profile is the following information that can be used to find more records:

  • Address: 385 Avenue of the Americas, also entrance at 135 Waverly Place
  • Buildings on Lot : 1
  • Block / Lot No. : 593 / 28
  • Landmark status: the building is in a landmark designated historic district, so may appear in the Landmark Designation report [for Greenwich Village].
  • NB 175-77


Detail from Plate 67, Maps of the city of New York surveyed under directions of insurance companies of said city / William Perris (1852-4)

This map shows the lot on the Northwest corner of Sixth Avenue and Waverly Place, once occupied by two buildings, 77 Sixth Avenue and 137 Waverly Place, before the current building, 385 Avenue of the Americas, was constructed in 1877. Property deeds and real estate news will often refer to the sites of buildings in terms of their geographical location (e.g. 50 yards from the Southeast corner of West 42nd and Fifth Avenue), especially where no block and lot number, or street number is yet available.

Plate 67 Maps of the city of New York surveyed und

Detail from Plate 17, Insurance maps of New York, Manhattan, V3, The Sanborn Map Co. of New York (1904).

This detail from a Sanborn fire insurance atlas of 1904 shows that the lot is now occupied by a single 4 story brick building, the same building that occupies the lot today. 

ManhattanV3 Plate 17 Sanborn 1904

Detail from Plate 35, Atlas of the Borough of Manhattan, City of New York, G.W. Bromley (1916)

This detail from a fire insurance map of 1916, was published by G.W. Bromley. It shows the borough block and lot number (593/28) which can be used to conform the identity of the building, and to find records associated with it in collections at various places. For instance, the Department of Buildings, the Municipal Archives, and the City Register's Office.


Detail from Plate 35, Manhattan land book of the city of New York, G.W. Bromley (1955)

This detail is from a 1955 fire insurance atlas that includes the current street name (Avenue of the Americas: not shown here) and building number, 385.

Manhattan land book of the city of New York. 1955