Census Tract

A census tract, census area, census district or meshblock[1] is a geographic region defined for the purpose of taking a census.[2] Sometimes these coincide with the limits of cities, towns or other administrative areas[2] and several tracts commonly exist within a county. In unincorporated areas of the United States these are often arbitrary, except for coinciding with political lines. Census tracts represent the smallest territorial entity for which population data are available in many countries.[3] In the United States, census tracts are subdivided into block groups and census blocks... In the U.S., census tracts are "designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions" and "average about 4,000 inhabitants". https://en.wikipedia.org/wiki/Census_tract#United_States

In New York City, there are 2,168 census tracts, which typically have a population of about 3,000-4,000 each, and an average land area of about 90 acres. (pdf)