3rd Missouri US Reserve Corps Infantry Regiment

The 3rd Missouri US Reserve Corps Infantry Regiment evolved from one of several unofficial pro-Unionist militia units formed semi-secretly in St. Louis in the early months of 1861 by Congressman Francis Preston Blair Jr. and other Unionist activists.

Although initially without any official standing, beginning on April 22, 1861, the Unionist regiments Blair helped organize were sworn into Federal service at the St. Louis Arsenal by Captain John Schofield acting on the authority of President Lincoln.

So many St. Louis Unionists mustered to volunteer, that after consultation with General-in-Chief Winfield Scott, and Secretary of War Simon Cameron, President Lincoln directed Captain Nathaniel Lyon to "enroll in the military service of the United States the loyal citizens of Saint Louis and vicinity, not exceeding with those heretofore enlisted, ten thousand in number, for the purpose of maintaining the authority of the United States; [and] for the protection of the peaceable inhabitants of Missouri.

As the Missouri militiamen were being march under guard back to the arsenal near the riverfront, angry crowds confronted the Federal forces and the confused situation soon devolved into rioting and gunfire.

Over 27 people were killed and the Camp Jackson Affair helped to polarize the state and send Missouri down the road to its own internal civil war.