In May of 2014, researchers from Washington University in St Louis and St Louis University put together a long report on racial health disparities in the St Louis area. It's largely a deep dive into the socioeconomic roots of these disparities, and includes this map highlighting the pattern of segregation by race and income levels in both the City and County of St Louis. On the left is the distribution of the African American population in the city and county, and on the right is the distribution of poverty:
The roots of neighborhood-level segregation go back to Jim Crow and old practices of redlining. Nowadays, a more likely culprit is exclusionary zoning where in-demand suburbs enact rules banning multi-family homes and small lots, seeking to make it impossible for the poor to come live there.