Short answers, pulled from the story.
The Compromise of 1877 withdrew federal troops from Louisiana, South Carolina, and Florida to end Reconstruction. This political deal allowed Southern Democrats to regain control of state governments through what historians call Redemption.
Mississippi adopted a new constitution in 1890 containing provisions requiring voters to pay poll taxes and pass literacy tests. These requirements were subjectively applied by white administrators to effectively disenfranchise most blacks and many poor whites.
Louisiana passed a new constitution in 1898 requiring applicants to pass a literacy test or certify owning $300 worth of property. By 1910, only 730 blacks remained registered, which was less than 0.5% of eligible black men compared to 130,334 in 1896.
The Supreme Court ruled in Giles v. Harris (1903) that protections of the Fourteenth Amendment did not apply to individual actions but only to state government actions. This decision upheld Alabama's disenfranchising constitution and left freedmen without legal recourse when facing private violence.
President Johnson signed the Civil Rights Act into law on the 2nd of July 1964 prohibiting segregation in public places and barring unequal application of voter registration requirements. It did not explicitly ban literacy tests used to disqualify blacks and poor white voters.