The South, since 1886 voted for the Democratic Party. How did the Republican Party displace the Democratic Party in the South starting in the 1950s?
The Republicans’ takeover of the South began because of racial reasons and continued because of cultural reasons.
Beginning at least in the 1950s (it is worth noting that the “Dixiecrats” ran in opposition to the regular Democratic Party in 1948) the South started to move away from the Democratic Party since the Democrats were becoming the party of civil rights. Much of the South was ardently segregationist. When the Democrats started to favor civil rights (this accelerated in the 1960s), the South moved towards the Republicans.
This trend became more pronounced in the 1960s as the continuing Civil Rights Movement, the Vietnam War, and the “counterculture” all worked to push Southerners away from the Democratic Party. The Democrats were coming to be identified with liberal cultural values. They were largely in favor of civil rights. Many of them, particularly by 1968, were against the Vietnam War. This allowed Richard Nixon to run a “southern strategy” in 1968 that helped him to win the election.
Today, religious and cultural conservatism (which come directly out of the 1960s) are largely responsible for the GOP’s extremely tight grip on the South.