How did the KKK in America use to be?

The Ku Klux Klan was a violent and virulent organization that took as its central belief that only White Protestant Christian individuals had a right and privilege to live and govern in the United States. They proceeded to threaten numerous minorities, especially African-Americans, with violence. As part of these threats, they would leave burning crosses on the lawns of "enemies". They would also perform lynchings to murder innocent members of the minority groups and incite fear and further violence through such acts.

In the Southern United States, from the 1880s to 1950s, the KKK was given almost free reign to sow unmitigated hatred and violence. The police oftentimes ignored or actively supported the KKK's acts of violence and terror since many Southerners were of the same mentality of human inequality that the KKK espoused.