4th Missouri Infantry Regiment (Union, 3 months)

The 4th Missouri 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. The organization that would become the Fourth Missouri was largely composed of ethnic Germans, who were generally opposed to slavery and strongly supportive of the Unionist cause. Although initially without any official standing, beginning on April 22, 1861, four militia 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. Secessionists and opponents of Unionist military organizing in Missouri in 1861 commonly referred to this unit as the "Black Guard" and "the blaggards".

The 4th Missouri Volunteer Infantry evolved out of a pre-existing German hunting society "Die Schwarzen Jäger". Upon entry into Federal service, the members of the new Fourth Missouri elected Nicolaus Schuettner colonel of the regiment. The new Missouri Volunteer regiments, subsequently elected (then) Captain Nathaniel Lyon as the brigadier general of the new brigade of Missouri volunteers. President Lincoln would later confirm Lyon's promotion from Captain to Brigadier general.