Look at the growth of the African American community like the effects of compound interest. Slaves started with essentially nothing when they were emancipated, then they lived under Jim Crow for 100 years which essentially meant their growth rate (you can say in terms of wealth or in terms of societal growth) was lower than that of the country’s average. Even after Jim Crow, they’ve still had to deal with things like police brutality or not receiving the same kinds of business opportunities that other races do, and the growth was also stilted by the problems inherent in their own community related to socioeconomic disparities left over from Jim Crow. (Tenements in Harlem or Detroit for example)
Essentially, the US created 200+ years ago a large caste of second class citizens and everything that’s been done since then, hasn’t helped them move from that caste. In some cases what’s what was done, had the effect of making things more difficult on them.