For those of us who like well-crafted census volumes, this is one of the better ones. Urbanized areas are rather complex constructs and frequently do not follow politcal boundaries. Instead they follow the more or less contiguous built-up areas surrounding American cities. The city and its surrounding suburbs must be at least 50,000 population and have 1,000 or more per square mile, and the central city must be 25,000, The area must lie within an SMSA (standard metropolitan statistical area), which are defined the Office of Management and Budget and not by the Census Bureau. From the maps, one can see how the Chicago Urbanized area was in 1970 defined along the extensions of the commuter railroads (the suburbs being "beads along the string"), and the infill had not fully happened, unlike Detroit which never had much of a commuter railroad network. Detroit is mostly composed of squarish blobs following the tonwship line of the Northwest Ordnance Survey of 1787. Coastal Floridian UA's stretch along the ocean as people want to live near the beach and not the inland swamp. I am glad I had the perspicacity to buy this type of Census mapping volume, as they have not been produced for the more recent censuses ( )