In Chicago at least, parking minimums were generally enacted as a package of policies to keep Black and Latino families out of neighborhoods. The Supreme Court struck down explicit racial zoning in 1917, which drove the creation of single-family zoning. Properties in Chicago were further "protected" by racial covenants, contractually preventing them from being sold to Black families. Those covenants were struck down in 1947. Immediately thereafter, Harland Bartholomew and his acolytes sold municipalities in Chicagoland (and around the country) on a package of parking minimums, setback requirements, and minimum lot sizes, all designed to address the prevailing concern at the time: that large single-family houses would be covertly converted into two-flats and rented to Black families.
Not 80 years ago. Into the 1980s and 90s. I can give specific examples.
A thing to keep in mind: sweeping zoning changes don't happen that often! Once every 20 years --- not exactly, but roughly --- is about right. And over the last "80 years", they've tended to ratchet. Most major metros have never had a period of pronounced housing deregulation (like other industries did in the 1970s and 1990s), so insane decisions made in the late 1940s remain in effect today, but get retconned as if the quality of live protections they promise were part of the original deal, and not a knock-on effect of a system of residential apartheid.
There is no question that restrictive zoning (and its constructive equivalents, like setback requirements) satisfy real, valid preferences of some existing homeowners. That's not the debate. The debate is whether states and localities owe those homeowners the satisfaction of those preferences, and at what cost. The existing residents advocating for density are essentially free-riding. I don't have to blame them for doing that to see that it's not something to valorize.
