It wasn't until the late 60's / early 70's that explicit racial discrimination was finally outlawed, and it's not a coincidence that exclusionary zoning took off immediately thereafter as a prima facie race-neutral way to achieve the same outcome.

...

But the largest legislative achievement of this emerging anti-growth coalition would be the Residential Rezoning of 1978, a project to implement stricter controls across all of San Francisco’s neighborhoods. In addition to creating 40-foot building-height limits for most residential areas, the legislation included new setback rules (regulating how far a building could be from the public right-of-way), low-density requirements (limiting the number of housing units in a given building), and overall design guidelines aimed at preserving entire neighborhoods in amber.

https://www.fastcompany.com/90242388/the-bad-design-that-cre...

Of particular concern was the fear that zoning would bring about racial and socioeconomic segregation in Massachusetts, which need not take the form of racial tests, as zoning could just as easily bring about segregation by regulating who could afford certain neighborhoods by income. Pro-zoning advocates... [went ahead anyways]

[0]: https://www.cambridgema.gov/~/media/Files/officeofthemayor/2...