The Ku Klux Klan bombed the 16th Street Baptist Church, an African-American church in Birmingham, Alabama, killing four girls and injuring at least 14 other people (memorial march pictured).

The Ku Klux Klan, sometimes referred to as the Klan, is an American Protestant-led white supremacist and far-right hate group. Historians widely identify it as one of the earliest terrorist groups in the United States, citing its organized use of violence and intimidation to influence political and social conditions, particularly in the post-Civil War South. Across its three major iterations, the Klan has operated as a secret society made up of multiple affiliated organizations that used threats, assaults, and killings to advance their aims. Over its various eras, its targets included African Americans, Jews, Catholics, and immigrants.