2nd Missouri Volunteer Infantry ( 3 months , 1861 ) The 2nd Missouri Volunteers 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 . The Second Missouri Volunteer Infantry included a significant number of members with military experience from service in Europe . Many had also participated in drill and marksmanship competitions in St . Louis ' s many Turnverein societies . The Second Missouri was an unusually large regiment , having two dedicated " Rifle Companies " in addition to its ten companies of infantry . Upon entry into Federal service the members of the new Second Missouri elected Henry Boernstein 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 . Military Service . On May 10 , 1861 the 2nd Missouri participated in the arrest of the Missouri Volunteer Militia drilling at Camp Jackson at Lindell Grove on the western border of St . Louis City . 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 . On June 15 , 1861 the Second Missouri participated in the unopposed occupation of the Missouri state capitol at Jefferson City , Missouri by Federal troops . Nine companies of the Second Missouri remained as the garrison at Jefferson City , under Colonel Boerstein who acted as interim military commandant of the city . Company " B " and Rifle Companies " A " and " B " continued up river in pursuit of fugitive Governor Claiborne Fox Jackson and the Missouri State Guard . At Boonville the three company battalion of the Second Missouri , fighting under the command of Captain Peter J . Osterhaus helped defeat the newly organized Missouri State Guard on June 17 in the short , one - sided Battle of Boonville . 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 Second Missouri garrison at Jefferson City made a number of expeditions and " scouts " into the counties near the state capital and the central Missouri River valley . A Second Missouri detachment from Jefferson City fought a small engagement with guerrillas at Mexico Missouri , on July 15 , 1861 . Osterhaus ' small battalion continued to campaign with Lyon , marching southwest to Springfield , eventually confronting a united Confederate and Missouri State Guard force near Springfield . 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 . Isolated and outnumbered after a second Federal element under Colonel Franz Sigel was routed , the Federals on Bloody hill fought the Confederate forces to a stalemate . 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 . Concerned about his force ' s ammunition supply , Sturgis decided to withdraw towards Springfield . Osterhaus ' men withdrew with the battered Federal force to Springfield , then to Rolla , continuing on to St . Louis . The regiment was mustered out of Federal service on August 31 , and the members were reorganized as the Second Missouri Volunteers ( 3 Years Service ) on September 10 , 1861 , under Colonel Friedrich Schaefer .