The Camp Jackson Affair was an incident of civil unrest in the American Civil War on May 10, 1861, when Union military forces clashed with civilians on the streets of St. Louis, Missouri, resulting in the deaths of at least 28 people and injuries to another 100. The highly publicized affair polarized the border state of Missouri, leading some citizens to advocate secession and others to support the Union, thus setting the stage for sustained violence between the opposing factions.
Union Captain Nathaniel Lyon hastily raised a militia, gained control of the arsenal (which was under the command of Peter V. Hagner), and started sending all but 10,000 rifles and muskets to Illinois. Lyon's militia had been recruited from German immigrants and members of the Wide Awakes political organization. The Germans in particular were unpopular with many native-born Missourians with Southern backgrounds, who deeply resented their anti-slavery views.
Around May 1, Missouri Governor Claiborne Jackson, who had favored the South but was neutral, called out the Missouri Militia for "maneuvers" about 4.5 miles northwest of the arsenal at Lindell's Grove (the current campus of St. Louis University on Lindell Boulevard) then outside the city of St. Louis in what has been called "Camp Jackson."
Lyon was to ascertain whether Confederate President Jefferson Davis had sent artillery (allegedly from the Baton Rouge, Louisiana arsenal) to the camp. According to popular account, Lyon had visited the camp disguised as a woman, more specifically as the mother-in-law of Frank Blair.
Tensions quickly mounted on the streets as civilians hurled rocks, paving stones, and insults at Lyon's troops. The heavily German Home Guard units were particularly targeted by the mob and shouts of "Damn the Dutch" were hurled at them from the crowd. Exactly what provoked the shooting remains unclear, but the most common explanation is that a drunkard stumbled into the path of the marching soldiers, and fired a pistol into their ranks, fatally wounding one German soldier, Captain Blandowski. The volunteers, in retaliation, fired into the crowd, killing some 20 people, some of whom were women and children, and wounding as many as 50 more.
The incident sparked several days of rioting and anti-German animosity in St. Louis. On May 11, another incident occurring at the intersection of 5th and Walnut streets saw German Volunteers fired at from windows and once again return fire into the mob. Col. Henry Boernstein, publisher of the Anzeiger Des Westens a prominent German Language newspaper in St. Louis and commander of the 2nd Regiment of Missouri Volunteers, 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 which caused many of the wealthy citizens of St. Louis to flee to either Illinois or the Missouri Interior.
Eventually the installation of martial law and the arrival of Federal Regulars to relieve the German volunteers would bring the situation to a conclusion but the impact of the Camp Jackson Affair left its mark on St. Louis permanetly.
On May 11, the Missouri General Assembly approved a measure to create the Missouri State Guard to resist the Union invasion with Sterling Price as its major general. The following day, Price and William S. Harney signed the Price-Harney Truce maintaining the earlier agreement to stay in the Union. On May 30, Harney was relieved of command by Abraham Lincoln for failing to deliver Missouri soldiers to the Union cause. Lyon was promoted to brigadier general and assigned command of all the Union forces in Missouri.
On June 11, Lyon and Jackson failed to reach an agreement to deliver the troops which was to result in Lyon pursuing Jackson and the elected government across the state until evicting Jackson and installing a new governor. In the process Lyon was to be killed in the Battle of Wilson's Creek.