Fun fact about readlining? My Great-Aunt and Great-Uncle owned a few dozen houses in Southern California in the 1910-1920 era. They helped set up what we would now call an HOA with a rider that no Protestant churches could be build within a certain area of the HOA. The riders specifically forbade non-Catholic families from living in the property. One of the I guess closing documents even had a place for your parish priest to sign as a character witness.
Parts of the old "little Italy" in San Diego banned non-Italian persons from living in a 20 square block area, a condition on a freeway being built through the neighborhood in the late 40's,
It feels weird, in a good way, that this is so shocking to people, and that these riders, now very illegal, still exist on paper from not that long ago.