December 26, 1862 The Largest Mass Execution in United States History Though the United States government and the Sioux conclude several treaties during the first half of the nineteenth century, relations deteriorate by 1862 when a Sioux uprising kills more than eight-hundred white settlers and soldiers in Minnesota. Military tribunals convict three-hundred-three Sioux prisoners of murder and rape and sentence them to death. President Abraham Lincoln commutes most of the sentences, but the public hanging of thirty-eight prisoners in Mankato, Minnesota, is still the largest mass execution in American history. The bodies are buried en masse in a trench in the sand of the riverbank.