The Camp Jackson affair, also known as the Camp Jackson massacre, was an incident during the American Civil War that occurred on May 10, 1861, when a volunteer Union Army regiment captured a unit of secessionists at Camp Jackson, outside the city of St. Louis, in the divided slave state of Missouri.
The newly-appointed Union commander in Missouri, Brigadier General Nathaniel Lyon, had learned that the ostensibly neutral state militia training in Camp Jackson was planning to raid the federal arsenal in St. Louis. After capturing the entire unit, Lyon marched the captives into town in order to parole them. En route, hostile secessionist crowds gathered, and after an accidental gunshot, Lyon's men fired into the mob, killing at least 28 civilians and injuring dozens of others. Several days of rioting throughout St. Louis followed. The violence ended only after martial law was imposed and Union regulars were dispatched to the city.
Lyon's actions ensured Union control of St. Louis and of Missouri as a whole for the rest of the war, but it also deepened the ideological divisions within a state that had originally sought to remain neutral in the larger conflict.
Missouri was a slave state, and many of its leaders were Southern sympathizers who favored secession and joining the Confederacy when the Civil War began. However, there were relatively few slaves and slaveowners in Missouri,  and only a minority initially favored secession.[ citation needed]
Nevertheless, by early 1861, both pro- and anti-secession factions in Missouri were organizing military and paramilitary forces. Secessionists organized as " Minutemen", often assisted by state officials. On February 13, Brigadier General Daniel M. Frost enrolled five companies of St. Louis-area Minutemen as the new 2nd Regiment of the Missouri Volunteer Militia. That same month, a new law banned militia activity outside the framework of the state-regulated MVM, forcing pro-Union activists to organize in secret.
On February 28, Missouri elected a Constitutional Convention to amend the state constitution and decide the issue of secession. On March 21, the Convention voted 98 to 1 against secession, but also voted not to supply weapons or men to either side if war broke out. The convention then adjourned.
On April 20, several days after the Battle of Fort Sumter, a pro-Confederate mob seized the Liberty Arsenal in Liberty, Missouri and expropriated about 1,000 rifles and muskets. This sparked fears that Confederates would also seize the much larger St. Louis Arsenal, which had nearly 40,000 rifles and muskets — the largest stockpile in any slave state.
Missouri was within the Department of the West, a geographical command of the United States Army commanded by Brigadier General William S. Harney, with its headquarters at Jefferson Barracks in St. Louis. Harney, an elderly career officer, wished to avoid open conflict with secessionist forces.
On April 23, the War Department replaced Harney with Captain Nathaniel Lyon as acting commander. Lyon, a passionate Unionist, immediately began enlisting and arming St. Louis Unionists as home guard "Missouri Volunteers", an action previously ordered by the Secretary of War but not acted upon by Harney. Most of Lyon's early recruits were "Forty-Eighters" and " Wide Awakes" (a marching society formed during the 1860 election by the Republican Party). According to one estimate, 80% of the volunteers in the first Missouri Volunteer regiments were German-American immigrants.  The anti-slavery foreign-born Germans were prejudicially targeted by pro-slavery native-born Missourians.
Lyon's next action, by order of the War Department, was to move the arms held in the St. Louis Arsenal out of reach of Missouri secessionists. Early in the morning of April 26, nearly 21,000 rifles were loaded on the steamer City of Alton, which carried them across the Mississippi River to Illinois. The remainder were held for issue to Lyon's Missouri Volunteers.
Missouri Governor Claiborne Fox Jackson had been elected in 1860 on the ticket of the pro-Union Douglas faction of the Democratic Party, but privately supported secession. Since the Constitutional Convention had voted against secession, Jackson and his fellow secessionists decided to carry it out by seizing St. Louis by force and presenting the people of Missouri with a fait accompli. The most significant obstacle was the St. Louis Arsenal, which was heavily fortified with thick walls.
In mid-April 1861, Jackson wrote to Confederate President Jefferson Davis, asking for heavy artillery to breach the walls of the arsenal. His letter was carried by militia officers Colton Green and Basil Wilson Duke.  Around May 1, Jackson called out part of the Missouri Volunteer Militia for "maneuvers" near St. Louis, under the command of Brigadier General Daniel M. Frost. The MVM set up "Camp Jackson", about 4.5 miles (7.2 km) northwest of the arsenal. The campsite was located at Lindell's Grove (then outside the city of St. Louis, and today part of the campus of St. Louis University on Lindell Boulevard).
Davis agreed to Jackson's request. On May 9, the steamer J. C. Swan delivered the Confederate aid: two 12-pound howitzers, two 32-pound siege guns, 500 muskets, and ammunition, in crates marked as Tamoroa marble. The munitions had been captured by the Confederates when they seized the Federal Baton Rouge Arsenal. MVM officers met the shipment at the St. Louis riverfront, and transported it to Camp Jackson, 6 miles (9.7 km) inland. 
Lyon suspected the Camp Jackson force of conspiring to attack the arsenal. His suspicions were confirmed by personal investigation after he visited Camp Jackson, allegedly disguised as an elderly woman.[ citation needed] On May 10, Lyon marched on Camp Jackson with about 6,000 Missouri Volunteers and U.S. Regulars. Lyon forced the surrender of the militia, taking 669 prisoners.
General Frost reported that his command was "deprived of their arms, and surrendered into the hands of Captain Lyon. After which, whilst thus disarmed and surrounded, a fire was opened upon a portion of it by his troops, and a number of my men put to death, together with several innocent lookers-on--men, women, and children." 
Lyon placed the captured soldiers under arrest, and began marching them under guard to the arsenal, where they were paroled and ordered to disperse. But the lengthy march was seen as humiliating by pro-secession residents of the city. Angry secessionists shouted insults at the Union troops, and threw rocks and debris at them. Units composed predominantly of ethnic Germans were particularly targeted, with shouts of "Damn the Dutch!" 
This eventually led to gunfire. Exactly what provoked the shooting remains unclear, but the most common explanation is that a drunkard stumbled into the path of Lyon's marching soldiers and fired a pistol into their ranks, fatally wounding Captain Constantin Blandowski of the 3rd Missouri Volunteer Infantry. [a] The Volunteers, in reaction, fired over the heads of the crowd, and then into the crowd. Some 28 civilians were killed, including women and children; more than 75 were wounded. 
The incident sparked several days of civil unrest in St. Louis. On May 11, Volunteers were fired upon from windows at 5th and Walnut streets; they returned fire into the mob. Colonel Henry Boernstein, commander of the 2nd Missouri Volunteer Infantry and publisher of the Anzeiger des Westens, a German-language newspaper in St. Louis, remarked in his memoirs that he gave several of his men leave to visit their families on the morning of May 11 and that "Most of them did not return... until it grew dark, with clothing torn, faces beaten bloody, and all the signs of having suffered mistreatment... Two of them never returned and they were never heard of again." 
Rumors spread throughout the city that the Germans were planning to murder the American population of the city; many wealthy St. Louisans fled to Illinois or the Missouri interior.[ citation needed] Martial law was imposed, and with the arrival of federal regulars to relieve the German volunteers, the violence came to an end.
Governor Jackson had previously proposed a "Military Bill" which would put the state on a war footing, create a new state military force, and grant the Governor broad executive powers. The bill had stalled at first, but on May 11, the day after the Camp Jackson affair, it was passed by the Missouri General Assembly, creating the Missouri State Guard with Major General Sterling Price as its commander. Unionists described the bill as a "secession act in all but name". Critics also observed that since it stated that all adult men were to be considered reserves of the State Guard, and granted the Governor wide powers as commander of the Guard, it had the effect of making Governor Jackson dictator of the state.
William S. Harney was reinstated as Commander of the Western District and met with Price on May 21. They signed the Price–Harney Truce, which left the federal military in charge of St. Louis and allowed Price's state militia to maintain order in the rest of the state. Many Missouri Unionists considered the agreement a capitulation to Jackson and the secessionists and lobbied President Abraham Lincoln for Harney's removal from command. Unionists outside of St. Louis reported harassment by secessionists, despite Harney's implicit understanding that the Missouri State Guard would protect them, and many fled to St. Louis for refuge.
Frank Blair was a well-known Republican leader and former U.S. Representative from St. Louis, as well as a recently promoted colonel. Lincoln authorized him to relieve Harney at his discretion. On May 30, Blair relieved Harney and permanently replaced him with Lyon. Lyon was promoted to Brigadier General and assigned command of all Union forces in Missouri.
On June 11, Lyon met face-to-face with Jackson, Price and their aides at the Planter's House hotel in St. Louis. They argued for four hours (much of it over Jackson's powers under the "Military Bill") before Lyon abruptly ended the meeting, declaring "Rather than concede to the State of Missouri for one single instant the right to dictate to my government in any matter however important, I would see you, and you, and you, and you, and every man, woman, and child in the State, dead and buried! This means war. In an hour one of my officers will call on you and conduct you out of my lines." 
Jackson returned to the state capital at Jefferson City. Lyon delivered federal troops by steamboat to Jefferson City on June 12, and Jackson fled west to join newly assembled State Guard troops near Boonville. Lyon's men occupied the capital without resistance, and pursued Jackson with approximately 1,400 volunteers and U.S. Army regulars. Against the advice of his senior officers, Jackson exercised his authority as Commander-in-Chief and ordered the State Guard to make a stand at Boonville. In the resulting Battle of Boonville on June 17, Lyon's troops routed the State Guard. Jackson, the State Guard, and a few secessionist state legislators escaped to southwest Missouri, near the Arkansas border, leaving most of the state under federal control.
The Constitutional Convention reconvened on July 22 and declared the office of Governor vacant due to Jackson's absence. [b] The Convention then voted to appoint former Chief Justice of the Missouri Supreme Court and conservative Unionist Hamilton Rowan Gamble as Governor of the Provisional Government of Missouri. Gamble's government was recognized by the Lincoln administration.
Nativism, mistrust of the federal government, fears for and of slavery, and states' rights issues all played roles in provoking the Camp Jackson affair. The incident immediately polarized the state between Union and Confederate supporters. Where previously most Missourians had advocated neutrality, many were now forced to take sides.
Some Missourians had attempted to find compromise as "Conditional Unionists", who opposed secession but with conditions: that slavery not be interfered with, and that no "coercion" or military force be used against the seceding states of the Confederacy. After the Camp Jackson affair, many of these "Conditional Unionists" became full Confederate supporters, such as former Governor Sterling Price.
Nonetheless, Lyon's actions ensured Union control of Missouri. After the war, the Missouri Volunteers were praised as "saviors of Missouri."
- List of incidents of civil unrest in the United States
- St. Louis in the American Civil War
- Missouri in the American Civil War
- Although usually described as "German", Blandowski was ethnically Polish, born in Upper Silesia, on the German side of the Russo-German frontier. He received his military training in Germany, served with the French Foreign Legion, and fought for the Hungarian rebels in the failed Hungarian Revolution of 1848. After emigrating to the U.S., he was active in the Turnverein movement in St. Louis. Despite his Polish ethnicity, he was embraced by the German-American community as a martyr and a symbol of ethnic-German devotion to the Union. 
- It should be noted that 20 of the 99 members of the Constitutional Convention were not present, having retreated to the southwest with Jackson, and so did not participate in the vote.
- Dr. Lorenzo J. Greene; Antonio F. Holland; Gary Kremer. "The Role of the Negro in Missouri History, 1719-1970: Slavery in Missouri". Official Manual - State of Missouri, 1973-1974. Lincoln University. Retrieved 22 March 2017.
- Williams, Scott. "The role of German immigrants in civil war Missouri". mcwm.org. St. Louis, MO: Missouri Civil War Museum. Archived from the original on 2012-03-03. Retrieved 2011-01-10.
- Gerties, Louis S., Civil War St. Louis, University of Kansas Press, 2001, p93
- Parrish, William E, Frank Blair: Lincoln's Conservative, University of Missouri Press, 1998, pp 100
- Report of Brig. Gen. Daniel M Frost, Missouri State Militia, May 11, 1861, War of the Rebellion, Series 1, Volume 3, p.7.
- Covington, James W. (1943). The Camp Jackson Affair, 1861 (master's thesis). St. Louis University.
- Burton, William L. (1998). Melting pot soldiers: the Union's ethnic regiments. North's Civil War. 4 (2nd ed.). New York: Fordham University Press. ISBN 9780823218271.
- Sandie Grassino and Art Schuermann, Jefferson Barracks (2011), p.33.
- Börnstein, Heinrich (1997). Rowan, Steven, ed. Memoirs of a nobody: the Missouri years of an Austrian radical, 1849-1866. Translated by Rowan, Steven. St. Louis: Missouri Historical Society Press. p. 303. ISBN 9781883982201.
- Albert Castel, General Sterling Price and the Civil War in the West, p.24
- Civil War reenactors of the Turner Brigade of Missouri Volunteers. They include elements of the 1st Missouri Light Artillery, direct descendants of the 1st Missouri Volunteer Infantry, which participated in Camp Jackson
- Missouri Civil War Museum discussion of the Camp Jackson Incident, its origins and effects.