Here's a bit of trivia sure to curb the cheer at your next Christmas party: The Ku Klux Klan, the United States' most infamous hate group, was founded on Christmas Eve 1865.
The secret society emerged in the wake of the Civil War during a period known as Reconstruction. That's when the federal government basically told the South what they had to do to be readmitted to the Union. Essentially, they wanted the old secessionist leaders to guarantee full equality to blacks, which, at the time, didn't sit well with many Southerners [source: PBS, Reconstruction].
It was into this climate that six Confederate veterans met in Pulaski, Tennessee, to form an organization that would fight back against these changes through fear and intimidation. Led by "Grand Wizard" Nathan Bedford Forrest, a former Confederate general, this group quickly gained popularity as it threatened, assaulted, raped and lynched thousands of blacks and the Republican carpetbaggers who supported them. The group was so violent that Congress passed the Ku Klux Klan Act of 1871, which gave the president the authority to use military force against the organization. The Supreme Court eventually ruled the law unconstitutional in 1882, but by then, Reconstruction was over and the KKK's influence had waned [source: PBS, KKK].
Since then, the KKK has experienced a couple of resurgences, first in the 1920s and again in the 1960s. Today, numerous splinter groups using the Klan name boast somewhere between 5,000 and 8,000 members [source: Southern Poverty Law Center].