What happened here? It’s almost like a 1:1 reverse.
1920
1964
Northern Louisiana is like the rest of the Deep South - it was solidly and faithfully Democratic for a long, long time, even in Republica landslides such as 1920, but as Democrats embraced civil rights, they began supporting candidates who were less pro-civil rights (i.e., not Democrats). 1964 was the epitomy of this as LBJ was staunchly pro-civil-rights and Barry Goldwater (though well-intentioned) was against, leading to many ancestrally Democratic counties - including those in northern Louisiana - to swing massively rightwards and support Goldwater (in many cases, the first time ever these counties voted Republican).
Don't know about Southern Louisiana but it appears to have been more Catholic and less 'Deep South' in culture, also more urban, and thus less extreme and more prone to voting the way the nation did (thus in 1920 backing Harding, who won in a landslide, and in 1964 LBJ, who similarly won in a landslide).
