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 each entity. By filling out the BAS questionnaire, the respondent provides the latest information on the legal name and description of the MCD.

The MCD boundaries used in the 1990 census were those legally in effect on January 1, 1990. The Census Bureau asks each BAS respondent if there were any boundary changes, and if so, to draw them on the maps provided. It also asks the MCD or county official to sign a statement certifying that the boundaries depicted on the map are shown correctly.

During the 1980s, some MCDs disorganized; that is, they lost their legal status as organized units of local government and reverted to the status of unorganized area. By contrast, some other areas that had been UTs in 1980 became organized units of local government. Because of these disorganizations and organizations, the Census Bureau had to update its geographic inventory. New UTs were identified, some existing UTs were combined or split, and there were boundary revisions to ensure that UT boundaries continued to follow visible features.

For the most part, the revisions made to CCDs in preparation for the 1990 census were minor. There were, however, some significant changes as a result of the establishment of census tracts and BNAs. The Census Bureau encouraged the local CSACs and the State coordinators to use the 1980 CCD boundaries as part of the new census tract or BNA framework wherever possible. In some instances, new 1990 census tracts or BNAs were delineated without regard to previously existing CCD boundaries. The Census Bureau then revised or totally redelineated CCD boundaries for the 1990 census to coincide with the new census tract/BNA boundaries.

The Census Bureau uses a system of geographic identification codes—geocodes—to identify every geographic entity for which it reports data. County Subdivisions8-27