In early December, 303 Sioux prisoners were convicted of murder and rape by military tribunals and sentenced to death. Some trials lasted less than 5 minutes. No one explained the proceedings to the defendants, nor were the Sioux represented by a defence in court. Pres. Abraham Lincoln personally reviewed the trial records to distinguish between those who had engaged in warfare against the U.S., versus those who had committed crimes of rape and murder against civilians.
Henry Whipple, the Episcopal bishop of Minnesota and a reformer of U.S. policies toward Native Americans, urged Lincoln to proceed with leniency. On the other hand, General Pope and Minnesota Senator Morton S. Wilkinson told him that leniency would not be received well by the white population. Governor Ramsey warned Lincoln that, unless all 303 Sioux were executed, “[P]rivate revenge would on all this border take the place of official judgment on these Indians.” In the end, Lincoln commuted the death sentences of 264 prisoners, but he allowed the execution of 39 men.
This clemency resulted in protests from Minnesota, which persisted until the Secretary of the Interior offered white Minnesotans “reasonable compensation for the depredations committed.” Republicans did not fare as well in Minnesota in the 1864 election as they had before. Ramsey (by then a senator) informed Lincoln that more hangings would have resulted in a larger electoral majority. The President reportedly replied, “I could not afford to hang men for votes.”
One of the 39 condemned prisoners was granted a reprieve. The 38 remaining prisoners were executed by hanging on December 26, 1862, in Mankato, Minnesota, in what remains the largest mass execution in American history.