As US elections draw near, it is instructive to learn a bit about how many races for House seats may be decided.

Gerrymandering with examples. You may notice that most of the examples are Republican drawn districts designed to 'pack' or diminish minority voters so that the effect of Black or Hispanic votes is limited. In one case...in N. Carolina... it actually allowed there to BE a Black member, while assuring it would be hard to have more than one.
In other cases, it just makes rural/city divisions more obvious.