During these decades, Republicans worked hard to protect the civil rights of the Blacks in the South. In Congress, the Republicans made the Civil Rights Act of 1866, the Civil Rights Act of 1871, and the Civil Rights Act of 1875 into law.
By the end of that century, however, the pro-slavery Democrats began to take power in the South.
As the Democratic Party asserted itself, it found ways to prevent African-Americans from voting. By the early 1900s, fewer Blacks were voting in the South than in the late 1800s.
With fewer African-Americans voting, the Democrats began to win elections in the South. Blacks had traditionally voted Republican.
The Democratic Party accumulated a string of victories by preventing African-Americans from voting in the South, as historian Patrick Buchanan notes:
In the two presidential campaigns of Wilson and the four of FDR, Democrats swept every Confederate state all six times. The Democratic candidate in 1924, John W. Davis, carried every Confederate state and, with the exception of Oklahoma, only Confederate states. Truman took seven Southern states to Strom Thurmond’s four. Dewey got none. In 1952 and 1956 most of the electoral votes Adlai Stevenson got came from the most segregated states of the South.
Some of the Democratic presidential candidates spoke in favor of segregation, like Woodrow Wilson. Some of the candidates were silent on the subject, like FDR, but allied themselves with segregationist vice-presidential candidates.
John Davis, the Democratic candidate for president in 1924, was an attorney who argued for segregation before the Supreme Court in the Brown v. Board of Education of Topeka in 1954.
The Republicans did not give up. They worked to help Black voters get back to the polls.
Against opposition from the Democrats, the Republicans in Washington passed the Civil Rights Act of 1957 and the Civil Rights Act of 1960, both of which were signed into law by Republican President Eisenhower.
The Republicans continued with the Civil Rights Act of 1964 and the Civil Rights Act of 1968. The Voting Rights Act of 1965 helped millions of African-Americans get their right to vote.
The return of Blacks to the voting booth eventually began to break the stranglehold which the Democratic Party held on the South. Over the next few decades, the monopoly held by the Democrats in southern politics ended.