Col. John M. Harrell, Confederate Military History, a library of Confederate States Military History: Volume 10.2, Arkansas
Clement Anselm Evans, Ed.

[19] Congress, colonel in the Mexican war, and governor of Missouri, and was a firm supporter of the cause of the Union. His earnest wishes and efforts were to have his State kept in a condition of neutrality, which should spare it from the devastations of war. But in the absence of General Harney from the department, a camp of State militia, under Gen. G. M. D. Frost, unarmed, and near the city of St. Louis, May 10th, was enjoying a holiday with a great many visitors from St. Louis looking on, when it was suddenly surrounded by a force of United States regulars and some German city companies under command of Capt. Nathaniel Lyon, commandant of the United States post at St. Louis. The non-resisting militia were taken prisoners. Captain Lyon, a New Englander and a fanatical abolitionist, was wrought up to believe that these militia exercises meant ‘treason’ to the government. Disregarding General Harney's compact, or believing it violated, he had determined to break up the militia camp. By some misunderstanding, while a large number of citizens were witnessing the marching off of their fellow citizens as prisoners of war, under Lyon's guard, one of the German military companies fired into these citizens, killing about 20, among whom were women and children. Lyon's action met the approbation of Lincoln. He was promoted and placed in command of the department of the West, vice General Harney, transferred to another field. General Lyon was an aggressive, enthusiastic supporter of the administration, and an unrelenting foe to its opponents. He scouted the idea of neutrality for Missouri, and scorned the proposition of Governor Jackson to disarm the militia and bind himself, as governor of the State, to call on the President in case of disturbance, because Governor Jackson had indignantly refused ‘to furnish troops for the subjection of the South.’ Jackson and Price were in earnest; but ‘neutrality’ was impracticable, and the proposition to maintain it subjected Missouri to four years of bloodshed