>I don't think that's actually true, at least not in the current century. What happened is they created maps to advantage Party A, and black people tend to vote as a near-monolith for Party B, which had the side-effect of electing fewer of black people's preferred Party B candidates.

You are free to think that. You need to remember, though - Alabama only had its first black representative in 1992, and that only happened because of a lawsuit reorganizing districts. In a non-racist system this would be a surprise because the black population is over 1/4th of the state and is geographically compact.

Either way, the effect of the districting is to dilute the voting power of the black population in favor of the white population. That's not legal to do, for good reason; states in the 20th century masked racial gerrymandering to hide their intent. See City of Mobile.