The Sacking of Osceola was a Kansas Jayhawker initiative on September 23, 1861, to push out pro-Southern elements at Osceola, Missouri. It was not authorized by Union military authorities but was the work of an informal group of pro-Union Kansas "Jayhawkers". The town of 3,000 people was plundered and burned to the ground, 200 slaves were freed and nine local citizens were executed.
The climax of the campaign was on September 23, 1861, at Osceola, where Lane's forces drove off a small Southern force and then looted and burned the town. An artillery battery under Capt. Thomas Moonlight shelled the St. Clair County courthouse. According to reports, many of the Kansans got so drunk that when it came time to leave they were unable to march and had to ride in wagons and carriages. They carried off with them a tremendous load of plunder, including as Lane's personal share a piano and a quantity of silk dresses. Lane led hundreds of slaves to Kansas and freedom. The troops moved Northwest and arrived at Kansas City, Missouri, on September 29, to pursue Price as he retreated south through the state.
Osceola was plundered with Lane's men freeing 200 slaves and taking 350 horses, 400 cattle, 3,000 bags of flour, and quantities of supplies from all the town shops and stores as well as carriages and wagons. Nine local men were rounded up, given a quick drumhead court-martial trial, and executed. All but three of the town's 800 buildings burned; the town never fully recovered.