Census tract

A census tract, census area, or census district is a particular community defined for the purpose of taking a census. Most often, these coincide with the limits of cities, towns, and townships. In unincorporated areas these are often arbitrary, except for coinciding with county lines.

Alaska

A census area is similar to a borough in the U.S. state of Alaska, with the following exceptions:

Its name and boundaries are defined by the United States Census Bureau, not by the State of Alaska.
It contains no area-wide government; therefore, it does not contain a capital (borough seat) city.