Description: 1990 Census Tracts from the Michigan Geographic Framework (MGF) base map. Census tracts are small areas created for statistical purposes that usually average about 4000 people.
Description: 1990 Block Groups from the Michigan Geographic Framework (MGF) base map. Block groups (BG’s) are combinations of census blocks within a census tract or BNA that share the same first digit in their identifying numbers. For example, BG 3 within a particular census tract comprises all blocks numbered between 301 and 399. A census tract or BNA contains a maximum of nine BGs. BG90 consists of the 6 digit tract number followed by the 1 digit block group number.