Zoning is in the history sweet spot: Recent enough that we have well-preserved records of its origins and use. But old enough that we have had time to study the

Zoning is in the history sweet spot: Recent enough that we have well-preserved records of its origins and use. But old enough that we have had time to study the effects in practice, regardless of original intent. Widespread enough that we can know any effects were not hidden variables from local geography or politics. But not universal, so we can compare the effects over time with and without it. That's all to say that it is well understood by people who study zoning in the US, of which there are plenty, that american racial dynamics are central in the history and use of zoning. It was not always used intentionally for segregation, but it was used for that very frequently over a long enough period of time that you can't consider it incidental to the practice. If you look to the early 20th century you can read the discussions people were having at the time about it: letters, and op-eds, and sometimes the ordinances themselves explicitly discuss the racial justifications. At the time racial segregation was well within the national overton window, they did not have a reason to hide to hide this motivation and so they did not. Later on it gets more complicated.