By the 1960s and ‘70s, light blue areas still accounted for most of the developed footprint, but they were losing ground.
A growing area saw new housing dominated by 2 to 49 unit structures, and the number of red Census tracts in which large multifamily structures accounted for most new homes increased as well. In addition, a scattering of Census tracts begin to show up in dark blue. Some of them – those which appear undeveloped (white) in the previous map – indicate extremely low-density residential development in formerly undeveloped areas, but most of them reflect previously developed suburban areas whose new home production essentially stalled.

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