(Not) Understanding the Racial, Economic, and Migratory History of Two Midwestern Cities

Here is a story that I wanted to confirm with data:

Benton Harbor, Michigan, used to be more white than it is now. At some point (likely in the late-1960s/early-1970s), the racial proportions of the city shifted, presumably as whites with the requisite economic and social capital fled the city, leaving behind poor blacks without the resources to relocate. Conversely, Saint Joseph, Michigan, Benton Harbor's "Twin City" (the height of unintendedly satirical titles) has become more solidly white and affluent over that period. In short, Benton Harbor's destitution is a story of White Flight across the river into Saint Joseph.

It's a simple hypothesis; however, the data don't seem to be (readily) available to tell this story.  Both Benton Harbor and Saint Joseph are in the same county (i.e. Berrien) and have generally been counted in the same metropolitan statistical area by the Census, which means that it is nearly impossible--at least for a person without specific training in historical demography and a lot of free time--to disentangle the two cities. (If you are reading this and know how to glean the data, please contact me.)

It makes me wonder if this is part of the reason that the two cities have been able to linger for so long in their highly unequal socioeconomic states. If it were easier to demonstrate the social history, perhaps it would have been easier to overcome.

Regardless, here is the history as I see it:
Benton Harbor is currently nearly 90% black and more than 40% impoverished (cite). Saint Joseph, on the other hand, is currently nearly 90% white and less than 7% impoverished (cite). This is the causal chain that I think led to this:

slavery → Jim Crow laws in the South→ Great Migration → deindustrialization → White Flight → Benton Harbor

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Special thanks to Philip Cohen for his help via Twitter pointing me to possible data and Tiffany Julian via Facebook for her help pointing out the limitations of the data.

Full disclosure: I spent the first 18+ years of my life in St. Joe and still have family and friends living there, hence my interest.