The Battle of Camp Jackson was fought on May 10, 1861. When the Missouri Volunteer Militia led by General Daniel M. Frost seized the St. Louis Arsenal and attacked U.S. Regulars and Missouri volunteers led by Captain Nathaniel Lyon. Lyon was sent to Capture the Missouri Volunteer Militia.
Around May 1, Missouri Governor Claiborne Fox Jackson, who had been elected on the ticket of the (Unionist) Douglas faction of the Democratic party, but privately supported secession, called out the Missouri Volunteer 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, at an encampment christened "Camp Jackson" by the militiamen
Previously in mid-April 1861, Governor Jackson had sent two pro-secessionist militia officers (Colton Green and Basil Wilson Duke) to Confederate President Jefferson Davis, with a letter asking for heavy artillery with which to attack the St. Louis Arsenal. On May 9, the steamer 'J.C. Swon' delivered the Confederate aid: two 12 pound Howitzers; two 32 pound siege guns; five hundred muskets; and ammunition in crates marked as Tamoroa marble. The munitions had been captured by the Confederates when they seized the Federal arsenal at Baton Rouge. MVM officers met the shipment at the St. Louis riverfront, and transported it to Camp Jackson, six miles inland.
in May, Governor Claiborne Jackson who had favored the South but had publicly pledged to uphold Missouri neutrality (at least until open hostilities between the Federal Government and the CSA) called out the Missouri Volunteer Militia for "maneuvers" about 4.5 miles (7.2 km) northwest of the arsenal at Lindell's Grove (now the campus of St. Louis University) then outside the city of St. Louis in what has been called "Camp Jackson."
The Missouri Volunteer Militia led by General Daniel M. Frost seized the St. Louis Arsenal. U.S. Regulars and Missouri volunteers led by Captain Nathaniel Lyon. Lyon was sent to Capture the Missouri Volunteer Militia. Tensions quickly mounted on the streets as civilians hurled rocks, paving stones, and insults at Lyon's troops. The heavily German Missouri Volunteer 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 Captain Constantin Blandowski of the Third Missouri Volunteers. The volunteers, in reaction, fired over the heads of...and then into.... the crowd, killing some 28 people, some of whom were women and children, and wounding as many as 50 more. Ate the battle Lyon was killed and the yankees surrendered.
.Governor Jackson exploited the Affair to resubmit the stalled "Military Bill" which would put the state on a war footing, create a new state military force, and granted the Governor wide executive powers. On May 11, the Missouri General Assembly approved the measure, which created the Missouri State Guard to resist the Union invasion with Sterling Price as its Major General. 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 to be 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. The following day, Major General Price and Brigadier General William S. Harney (Commander of the Western District, which included Missouri) signed the Price-Harney Truce leaving the Federal military in charge of St. Louis, and allowing state forces to maintain order in the rest of the state. Many Missouri unionists considered the agreement to be a capitulation to Jackson and the secessionist faction. Unionists outside of St. Louis reported harassment by secessionists, many fleeing to St. Louis for refuge. On May 30, Harney was relieved of command by Congressman/Colonel Francis P. Blair, Jr who had previously been granted the right to do so at his discression by President Lincoln.