Robert Moses being the most egregious direct example, but Plessy v Ferguson enshrining racist segregationist laws around transportation which then provided precedent to spread to other segregationist laws.
Is racial segregation was by design (100% non Whiltes) or just happed due to economic factors (majority of non whites happens to be in this category)?
As an example, banks refused to lend in minority neighborhoods, so unlike for white Americans who used loans to bid up houses owned by white Americans and got wealth that way, Black Americans actually experienced negative housing wealth growth. Those areas are still poor, but now banks don’t lend in them because they’re not profitable, even though the reason they are not profitable is that they were never lent to in the first place.
When Black people managed to build parallel financial systems and economies to provide them wealth, usually they got their properties burned down or firebombed for their trouble. https://en.wikipedia.org/wiki/Tulsa_race_massacre