The Palmyra Massacre is an incident that took place 150 years ago today in Palmyra, Missouri. On October 18, 1862, during the Civil War, ten Confederate prisoners of war were executed in reprisal for the abduction of a local Union supporter, Andrew Allsman. The officer who ordered the execution, Colonel John McNeil, was later known as the "Butcher of Palmyra". On the evening of October 17th, 1862, ten prisoners were selected. Five were from the jail in Hannibal and five from the jail in Palmyra. None of them had any connection with the disappearance of Allsman.  All ten were executed on October 18th by a firing squad of thirty soldiers from the Second Missouri State Militia.

The Palmyra Massacre attracted nation-wide attention and was the subject of discussion in the cabinet of President Lincoln. The Palmyra Confederate Monument Association erected a granite monument on the grounds of the Palmyra Courthouse on February 25, 1907. The monument lists the men executed who were Capt. Thomas A. Sidenor, of Monroe County; Willis J. Baker, Thomas Humston, Morgan Bixler, John Y. McPheeters and Hiram T. Smith of Lewis County; Herbert Hudson, John M. Wade and Marion Lair of Ralls County and Eleazer Lake of Scotland County.

The Monument is still standing and is located on the grounds of the Marion County Courthouse. There is no charge to visit the monument.