Following the passage of the first Enforcement Acts, written to protect the civil rights of the formerly enslaved, Congress created a bipartisan committee in 1871 to investigate reports of vigilante violence against freed people and their white allies in the states of the former Confederacy. The next year, the Joint Select Committee to Inquire into the Condition of Affairs in the Late Insurrectionary States released its report, a 13-volume collection of testimony from 600 witnesses, totaling more than 8,000 pages.

The men and women who spoke to the committee attested to pervasive violence and intimidation. There were innumerable reports of whippings and beatings and killings. “Tom Roundtree, alias Black, a negro, murdered by a Ku-Klux mob of some fifty or sixty persons, who came to his house at night on the 3rd of December last, took him out, shot him, and cut his throat,” reads a typical entry in the volume devoted to Klan activity in South Carolina. “James Williams,” reads another entry in the same volume, “taken from his home at night and hung, by Ku-Klux numbering about forty or fifty.”

There were also, as the historian Kidada E. Williams shows in “I Saw Death Coming: A History of Terror and Survival in the War Against Reconstruction,” accounts of terrible sexual violence. Williams describes one attack in which a group of vigilantes whipped their victim, Frances Gilmore of Chatham County, N.C., “set fire to her pubic hair, and cut her genitals.”

Because of these reports and others collected by lawyers, journalists and other investigators, the American public had “access to more information about the Ku-Klux than about almost any other person, event, phenomenon, or movement in the nation,” the historian Elaine Frantz Parsons observes in “Ku-Klux: The Birth of the Klan during Reconstruction.” Between government reports, testimony from witnesses, the confessions of actual Klansmen and the physical evidence of violence and destruction, it would seem impossible to deny the awful scope of Klan terror, much less the existence of the Klan itself.