The yellow areas explain a lack of multi-unit development during that era. Yellow areas were considered by the banks to be "imminent to decline." If you look at what areas of Hackensack are red and yellow, it's a map of where multi-unit development WAS NOT built from 1938 through the 1940's, and perhaps a few years more. So for instance, you have multi-unit buildings from those years built in the southern part of Fairmount where the banks said OK to financing by builders (Hamilton & Franklin, on Clinton west of Clarendon, and the NE corner Clinton & Grand), but all multi-unit development stopped in the vicinity of Anderson Park (that was designated as a yellow area), and nothing multi-unit was built in the yellow areas further north in Fairmount. I wonder that the banks thought the northern parts of Fairmount were imminent to decline because houses being built were small and lots of working class Irish were moving in (say around Main & Catalpa), but Passaic Street, Hamilton Place, and Clinton Place (& vicinity) had much larger houses, and they were relatively new, and more white collar than blue collar, and at the time there were many more families of White Protestant background that the banks favored. The red-lining map provides a lot of evidence in terms of development patterns in Hackensack.