The Ku Klux Klan is a white supremacist group that opposes civil rights for African Americans, Jews, Catholics, immigrants, gays, and other racial, ethnic, social, and religious groups. The Klan was founded in 1866 in Pulaski, Tennessee by a handful of former Confederate soldiers. It began as a fraternal organization, providing support to Confederate widows and orphans, but changed its focus as the federal government imposed measures during the Reconstruction Era to end segregation.

In 1870, the Fifteenth Amendment extended the right to vote to black men. Outraged by this extension of civil rights to black citizens, the Klan transformed from a community service organization to a paramilitary group bent on denying black citizens access to the political process.

The Ku Klux Klan used a variety of tactics to intimidate their victims. They hid their identities under long white robes and pointed hoods, designed to represent the ghosts of vengeful Confederate soldiers. Klan members, who were exclusively white Anglo-Saxon Protestants, adopted Christian symbolism in their rituals. They are probably best known for the burning crosses they planted near the homes of the individuals they wished to intimidate. Other scare tactics included rallies on the periphery of black communities, night rides by gangs of Klansmen, and arson. When those strategies did not work, Klan members resorted to physical assault, including beatings, rape, and lynchings.

In 1871, Congress passed the Force Bill, outlawing the Klan as a terrorist group; hundreds of Klansmen were arrested and jailed. Membership in the Klan declined for a time, but not because of the government crackdown. As former Confederate state governments regained political control, racial segregation was re-established in the South.

There was a renewal of Klan activity during World War I, as many poor whites blamed their economic problems on African Americans, Catholics, and Jews. The group expanded to more than 20 states, using the same terrorist tactics as the original group. The Klan reached its peak in 1924, when it was estimated to have as many as five million members. It also became a political force to be reckoned with. The Alabama Robert E. Lee Klan No. 1, founded in 1916, had more than 200,000 members in the mid-1920s and reportedly controlled more than half of the white registered voters in the city of Birmingham. Many white ministers, judges, police officers, and other public officials joined. Any politician expecting to win election had to be a member. Hugo Black, a U.S. Supreme Court justice who voted in favor of the Brown v. Board of Education decision in 1954, was once a member in the 1920s. This second Klan collapsed as a result of infighting among its leadership and public outcry over its violence.

The third revival of the Klan occurred following World War II. During the Civil Rights movement of the 1950s and 1960s, Klan members committed countless acts of violence against blacks and sympathetic whites, including the murder of several civil rights activists and the famous bombing of the Sixteenth Street Baptist Church in Birmingham on September 15, 1963.

Today the Klan is estimated to have between 5,000 and 6,000 members. It continues to stage rallies, a right protected by the First Amendment's freedom of assembly clause. However, a recent Supreme Court decision, Virginia v. Black (2002), ruled that cross burning is not a form of expression protected by the Constitution. Said the Court: "We tolerate the expression of hatred because the First Amendment guarantees freedom of all expression, but we distinguish from true expression words and expressive conduct that are intended and likely to intimidate."