(10 ILCS 105/5)
As used in this plan, the following are the 1990 census geographic areas that
appear in the TIGER/Line files and other official data products and shall be
defined and construed as follows:
"Minor civil division (MCD)" means the legally defined subcounty area such as
a town or township.
"Census county division (CCD)" means an area delineated by the Census Bureau
in cooperation with State and local officials where Minor civil divisions do
not exist or are not adequate for reporting subcounty statistics.
"Census tract" means a small locally delineated statistical area within
selected counties generally having stable boundaries and, when first
established by local committees, designed to have relatively homogeneous
demographic characteristics. Census tracts do not cross county boundaries.
"Block numbering area (BNA)" means an area delineated cooperatively by the
State and the Census Bureau for grouping and numbering blocks in areas where
census tracts have not been established. Block numbering areas do not cross
"Block group" means a combination of census blocks sharing the same first
digit in their identifying numbers within a census tract of BNA. Boundaries
for block groups are not explicitly coded in the TIGER data base, but can be
derived from it.
"Census block" means a small, usually compact area, bounded by streets and
other prominent physical features as well as certain legal boundaries. Blocks
do not cross BNA, census tract, or county boundaries. Blocks are assigned
3-digit numbers, with a possible single letter suffix.
(Source: P.A. 89-563, eff. 7-26-96.)