Grant, Reconstruction and the KKK
At the time of Ulysses S. Grant's election to the presidency, white supremacists were conducting a reign of terror throughout the South. In outright defiance of the Republican-led federal government, Southern Democrats formed organizations that violently intimidated blacks and Republicans who tried to win political power.
The most prominent of these, the Ku Klux Klan, was formed in Pulaski, Tennessee, in 1865. Originally founded as a social club for former Confederate soldiers, the Klan evolved into a terrorist organization. It would be responsible for thousands of deaths, and would help to weaken the political power of Southern blacks and Republicans.
Racist activity in the South often took the form of riots that targeted blacks and Republicans. In 1866, a quarrel between whites and black ex-soldiers erupted into a full-fledged riot in Memphis, Tennessee. White policemen assisted the mobs in their violent rampage through the black sections of town. By the time the violence ended, 46 people were dead, 70 more were wounded, and numerous churches and schools had been burned. Just two months later, on July 30, a similar outbreak of violence erupted in New Orleans. This time, a white mob attacked the attendees of a black suffrage convention, killing 37 blacks and three whites who allied with them.
In this violent atmosphere, the Ku Klux Klan grew in size and strength. By 1868, the Klan had evolved into a hooded terrorist organization that its members called "The Invisible Empire of the South." The reorganized Klan's first leader, or "Grand Wizard," was Nathan Bedford Forrest, who had been a Confederate general during the Civil War.
White Southerners from all classes of society joined the Klan's ranks. In the name of preserving law and order in a white-dominated society, Klansmen punished newly freed blacks for a variety of reasons, including behaving in an "impudent" manner toward whites. They whipped the teachers of freedmen's schools and burnt their schoolhouses. But first and foremost, the Klan sought to do away with Republican influence in the South by terrorizing and murdering its party leaders and all those who voted for it.
In the time leading up to the 1868 presidential election, the Klan's activities picked up in speed and brutality. The election, which pitted Republican Ulysses S. Grant against Democrat Horatio Seymour, was crucial. Republicans would continue programs that prevented Southern whites from gaining political control in their states. Klan members knew that given the chance, the blacks in their communities would vote Republican.
Across the South, the Klan and other terrorist groups used brutal violence to intimidate Republican voters. In Arkansas, over 2,000 murders were committed in connection with the election. In Georgia, the number of threats and beatings was even higher. And in Louisiana, 1000 blacks were killed as the election neared. In those three states, Democrats won decisive victories at the polls.
Nevertheless, the Klan's violent actions proved to many Northerners that the South had not learned its lesson in the recent war. In this way, the Klan's activities actually backfired. People realized that harsher laws would have to be passed in order to stop the violence and protect Southern blacks. And those laws were soon in coming.
In the 1868 presidential election, Republican Ulysses S. Grant won the office with the slogan, "Let Us Have Peace." Republicans also won a majority in Congress. Many Northerners, disgusted by Klan violence, lent their support to the Fifteenth Amendment, which gave the vote to black men in every state, and the First Reconstruction Act of 1867, which placed harsher restrictions on the South and closely regulated the formation of their new governments.
Other legislation attacked the Klan more directly. Between 1870 and 1871, Congress passed the Enforcement Acts, which made it a crime to interfere with registration, voting, officeholding, or jury service of blacks. More than 5,000 people were indicted under these laws; a little more than 1,000 were convicted.
In 1871 Congress also passed the Ku Klux Klan Act, which allowed the government to act against terrorist organizations. Grant did not rigorously enforce these laws, although he did order the arrest of hundreds of Klan members. But with the overwhelming support of the Klan in the South, convictions proved difficult to obtain, and the financial panic of 1873 would distract the North from the problems of Southern racism. In 1882 the United States Supreme Court declared Ku Klux Klan Act unconstitutional.
https://www.pbs.org/wgbh/americanexperience/features/grant-kkk/