3rd Missouri Volunteer Infantry ( 3 months , 1861 ) The 3rd 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 Third 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 . Upon entry into Federal service the members of the new Third Missouri elected Franz Sigel 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 . The regiment , composed almost completely of ethnic Germans , was unusually large , with ten infantry companies and two rifle companies . Military Service . On May 10 , 1861 the Third Missouri under Colonel Blair 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 . After June 12 , 1861 the Third Missouri was part of a complex movement against the Missouri State Guard . On force , under Brigadier General Lyon moved up the Missouri River by steamer , to capture the State capital at Jefferson City . A second brigade , composed of the 3rd and 5th Missouri and two batteries of artillery moved into southwest Missouri under the overall command of Colonel Sigel , to cut off any Missouri State Guard troops which might move south before Lyon ' s advance . Colonel Sigel took his force to Rolla , thence to Springfield , Missouri arriving on June 25 . They marched to Neosho ( June 26 – 30 ) and were forced to retreat to Mt . Vernon in the face of a large force of State Guardsmen . Two companies of the Third Missouri who formed Sigel ' s rear guard were captured covering the retreat . On July 5 , Sigel ' s force of 1 , 100 met 4 , 000 State Guardsmen ( and 2 , 000 unarmed Guard recruits ) at the Battle of Carthage . Confronted with the large force of Guardsmen Sigel retreated in good order into Carthage and successfully disengaged and retreated back to Sarcoxie that night . The Third joined with General Lyon ' s force at Springfield , and participated in the August 10 Battle of Wilson ' s Creek . The Third was again part of a brigade ( with the Fifth Missouri ) under Colonel Sigel . Sigel ' s 2nd Brigade initially had significant success , attacking Confederate cavalry on the southeast corner of the southern camps ( at the Sharp Farm ) . After driving off these southern troops , Sigel halted his brigade across the Wire Road , above Skeeg ' s Branch ( Creek ) . However , Sigel positioned his artillery badly ( behind the military crest of the ridge ) and cautioned his men against accidentally firing on Federal troops he expected to be advancing south down the Wire Road ( the 1st Iowa Infantry was uniformed in grey ) . At this point , Confederate Brigadier Ben McCulloch lead an attack south down the Wire Road , with the respected Third Louisiana Infantry in fore . Skirmishers , officers , and Sigel himself mistook the Louisiana troops for the Iowa infantry allowing them to advance to point blank range before delivering a devastating volley into the confused Federal troops . Sigel shouted " they make a mistake " as his brigade was overrun . The majority of the shattered Third Missouri escaped , and eventually rejoined the Federal force retreating to Springfield , and then back to Rolla . From there the regiment was ordered back to St . Louis to be demobilized . The all companies of the regiment were mustered out by September 4 , 1861 . Elements of the 3rd Missouri Volunteers ( 3 Months Service ) were incorporated in the new 3rd Missouri Volunteer Infantry ( 3 Years Service ) under Colonel Isaac F . Shephard .