Every state gerrymanders. Mississippi is hardly alone on this.
>In the state of Ohio, a conversation between Republican officials was recorded that demonstrated that redistricting was being done to aid their political candidates. Furthermore, the discussions assessed race of voters as a factor in redistricting, because African-Americans had backed Democratic candidates. Republicans apparently removed approximately 13,000 African American voters from the district of Jim Raussen, a Republican candidate for the House of Representatives, in an attempt to tip the scales in what was once a competitive district for Democratic candidates.
http://en.wikipedia.org/wiki/Gerrymandering#United_States
That's coming at you from blue-collar freezing-cold northern Ohio.
Furthermore, "right after" the Civil Rights act was passed? It was passed a full 47 years ago.