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In preparation for the 1990 decennial census, the Census Bureau expanded the delineation of BNAs so that all counties (or statistically equivalent entities) not in the 1990 census tract program would have BNAs. To do this, it developed a program for the governments of States, American Indian tribes, Puerto Rico, and the Outlying Areas to participate in the delineation of BNAs and block groups. This effort paralleled the delineation, or review and update, of census tracts and block groups being undertaken by the census statistical areas committees.

The Census Bureau contacted State/territorial governors and requested that they designate an agency to coordinate the delineation of BNAs for the 1990 census. It offered them two options for participation in the 1990 BNA program. Under the first option, the State/territorial agency delineated the BNAs (in some instances, with assistance from interested county or local agencies). Under the second option, the Census Bureau delineated the BNAs and sent the delineations to the designated State/territorial agency for review and concurrence. Although many States chose one option or the other, several combined both approaches. In Florida and Illinois, the State governor declined to participate in the BNA program and the Census Bureau delineated the 1990 BNAs.

For the 1990 census, the Census Bureau recognized some census tracts and BNAs that did not conform completely to established criteria. This was due to a number of factors, including Census Bureau enumeration and tabulation requirements, TIGER System constraints, and special arrangements reflecting the unique needs of data users.

Data users first saw geographic products showing the 1990 census tracts and BNAs on the Precensus Local Review Maps. In some instances, they discovered a discrepancy between the location of the census tract or Census Tracts and Block Numbering Areas10-9