NYC Open Data: Borough-Block-Lot (BBL)

The pre 1900s boom in dense urban cities and suburban neighborhoods created the need and the desire to separate large plots of land into smaller subsections. This provided supply to meet housing demands, and liquidity to land owners. A landowner in New York could create many sellable pieces of land from one that was much larger. Slicing and dicing land in the 1850s until present day has made real estate investors a lot of money. This was, and is, common practice.

With land splitting and exchanging hands, the city needed a way to keep a record of where land was transferring hands, and how it had been partitioned. The solution to this problem was a method for land surveying described as block and lot.

Borough, Block, and Lot (BBL)

BBL's are always 10-digit values where the leading digit is the borough number(1-5), followed by a 5-digit block number, and a 4-digit lot number.

Notes:

• There are no duplicate BBLs

• There are high-block, and low-block min/max values available in data sets

• There are over 1,000,000 unique BBLs in NYC

• BBL numbers are exclusive to New York City

Borough

• Manhattan (borough code: 1)

• The Bronx (borough code: 2)

• Brooklyn (borough code: 3)

• Queens (borough code: 4)

• Staten Island (borough code: 5)

Block

The block number is supposed to be 5 digits, prefixed with 0's if necessary. In many databases you will see block as an n-digit value without 0 prefixes.

Example: 00001, 00123, 01234, 12345

Lot

4 digit number, prefixed with 0's if needed. In many databases you will see lot as an n-digit value without 0 prefixes.

Example: 0001, 0012, 0123, 1234