A voluntary 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 Second 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.
[1][2] The 2nd Missouri Infantry Regiment included a significant number of members with military experience from service in Europe.
Upon entry into Federal service the members of the new Second Missouri elected Henry Boernstein colonel of the regiment.
President Lincoln would later confirm Lyon's promotion from Captain to Brigadier general.
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.
At Boonville the three company battalion of the Second Missouri, fighting under the command of Captain Peter J. Osterhaus[3] helped defeat the newly organized Missouri State Guard on June 17 in the short, one-sided Battle of Boonville.
[4] While the Battle of Boonville was small by later war standards, it had major strategic consequences, driving the pro-secessionist forces into the southern part of the state and securing the Missouri River valley and communications across the state for the Federal government.
The resulting Battle of Wilson's Creek fought ten miles south of the city on August 10, 1861, was a bloody affair, and the second costliest in American history up to that time.
Osterhaus, by that time promoted to major, led his men in the fighting as part of Lyon's detachment of the Federal force on Bloody Hill.
[5] The battle ended only after General Lyon was killed leading the 1st Iowa Infantry against the Confederate right.
As the senior U.S. Army regular officer present, command devolved to Major Samuel D. Sturgis.
[6] Osterhaus' men withdrew with the battered Federal force to Springfield, then to Rolla, continuing on to St. Louis.
2nd Brigade, 3rd Division, Right Wing, XIV Corps, Army of the Cumberland, to January 1863.