The original Ku Klux Klan was founded on Christmas Eve, 1865. Established by Confederate veterans, it was one of many organizations founded with the purpose of defending Southern society (i.e. white supremacy) from the changes that seemed imminent in the aftermath of the Civil War. Klan members used terror and violence to intimidate African-Americans, and later turned their ire to "carpetbaggers" and white Southern collaborators. Essentially, as historian Eric Foner observed, the Klan was a
military force serving the interests of the Democratic party, the planter class, and all those who desired restoration of white supremacy. Its purposes were political, but political in the broadest sense, for it sought to affect power relations, both public and private, throughout Southern society. It aimed to reverse the interlocking changes sweeping over the South during Reconstruction...
Foremost among these changes was political power for freedmen, who received the right to vote via the Fifteenth Amendment. Klansmen sought to intimidate them and keep them from the polls, in addition to enforcing white supremacy.