Capture of Sedalia

At the outset of the American Civil War in 1861, the state of Missouri was a slave state. Governor Claiborne Fox Jackson supported secession, and activated the pro-secession state militia. The militia were sent to the vicinity of St. Louis, Missouri, where Brigadier-General Nathaniel Lyon dispersed the group using Union Army troops in the Camp Jackson affair on May 10. A pro-secession riot in St. Louis followed, in which several military personnel and civilians were killed or wounded. On May 12, Jackson formed a pro-secession militia unit known as the Missouri State Guard and placed Major-General Sterling Price in command.[lower-alpha 1] In June, Lyon moved against the state capital of Jefferson City and evicted Jackson and the pro-secession group of state legislators. Jackson's party moved to Boonville, although Lyon captured that city after the Battle of Boonville on June 17.[5]

In July, anti-secession state legislators held a vote rejecting secession. Brigadier General Ben McCulloch of the Confederate States Army joined Price's militia forces; the combined group defeated Lyon at the Battle of Wilson's Creek in southwestern Missouri on August 10.[6] After Wilson's Creek, Price drove northwards, capturing the city of Lexington. However, the Missouri State Guard retreated in the face of Union reinforcements, falling back to southwestern Missouri. In November, while at Neosho, Jackson and the pro-secession legislators voted to secede, and joined the Confederate States of America as a government-in-exile.[7] In February 1862, Price abandoned Missouri for Arkansas in the face of Union pressure, joining forces commanded by Major General Earl Van Dorn.[8] In March, Price officially joined the Confederate States Army, receiving a commission as a major general.[4] That same month, Van Dorn was defeated at the Battle of Pea Ridge, giving the Union control of Missouri.[9] By July 1862, most of the men of the Missouri State Guard had left to join Confederate States Army units.[10] Missouri was then plagued by guerrilla warfare throughout 1862 and 1863.[11]

National Park Service map of Price's Missouri Raid

By the beginning of September 1864, events in the eastern United States, especially the Confederate defeat in the Atlanta campaign, gave Abraham Lincoln, who supported continuing the war, an edge in the 1864 United States Presidential Election over George B. McClellan, who promoted ending the war. At this point, the Confederacy had very little chance of winning the war.[12] Meanwhile, in the Trans-Mississippi Theater, the Confederates had defeated Union attackers in the Red River campaign in Louisiana in March through May. As events east of the Mississippi River turned against the Confederates, General Edmund Kirby Smith, commander of the Trans-Mississippi Department, was ordered to transfer the infantry under his command to the fighting in the Eastern and Western Theaters. However, this proved to be impossible, as the Union Navy controlled the Mississippi River, preventing a large scale crossing.

Despite having limited resources for an offensive, Smith decided that an attack designed to divert Union troops from the principal theaters of combat would have the same effect as the proposed transfer of troops. Price and the Confederate Governor of Missouri Thomas Caute Reynolds suggested that an invasion of Missouri would be an effective offensive; Smith approved the plan and appointed Price to command the offensive. Price expected that the offensive would create a popular uprising against Union control of Missouri, divert Union troops away from principal theaters of combat (many of the Union troops previously defending Missouri had been transferred out of the state, leaving the Missouri State Militia to be the state's primary defensive force), and aid McClellan's chance of defeating Lincoln;[13] on September 19, Price's column entered the state.[14]

By September 24, Price's column had reached Fredericktown, where he learned that Pilot Knob and the St. Louis & Iron Mountain Railroad were held by Union forces under the command of Brigadier General Thomas Ewing Jr. Price had no interest in allowing an enemy force to operate in his rear while he advanced to St. Louis, so he sent two of his three divisions, under Brigadier General John S. Marmaduke and Major General James F. Fagan to Pilot Knob; the third division, under Brigadier General Joseph O. Shelby, operated north of the town. On September 26, Ewing fought off Fagan at Arcadia before withdrawing to the defenses of Fort Davidson. The next day, Price moved against the fort and offered Ewing surrender terms; the latter refused, as he was afraid of being executed for his unpopular issuance of General Order No. 11 the previous year. Holding out, the Union defenders repulsed multiple assaults, before slipping out of the fort at 03:00 on September 28. The Confederates suffered at least 800 casualties during the engagement and had their morale depressed, leading Price to abandon the attempt against St. Louis.[15]

After abandoning the St. Louis thrust, Price's army headed for Jefferson City, although the Confederates were slowed by bringing along a large supply train.[16] On October 7, the Confederates approached Jefferson City, which was held by about 7,000 men, mostly inexperienced militia, commanded by Brigadier General Egbert Brown. Faulty Confederate intelligence placed Brown's strength at 15,000, and Price, fearing another defeat like Pilot Knob, decided not to attack the city, and began moving his army toward Boonville the next day.[17] Boonville was in the pro-Confederate region of Little Dixie, and Price was able to recruit between 1,200[18] and 2,000 men.[19] Price, needing weapons,[19] then authorized two raids away from his main body of troops: Brigadier General John B. Clark Jr. was sent to Glasgow, and Brigadier General[lower-alpha 2] M. Jeff Thompson's brigade of Shelby's division to Sedalia.[21]

Thompson's command consisted of Shelby's Iron Brigade of Slayback's Missouri Cavalry Battalion, Elliott's Missouri Cavalry Regiment, the 5th Missouri Cavalry Regiment, and Collins' Missouri Battery; the force totaled around 1,200[22] or 1,500 men.[23] Two redoubts and some rifle pits defended the town.[22] The Union garrison of Sedalia consisted of two militia regiments: the 1st Missouri State Militia Cavalry and the 7th Missouri State Militia Cavalry.[24] Before daylight on October 15, Thompson's brigade, with Elliott's regiment in the lead, attacked the Union barricades.[22] Elliott quickly drove off Union pickets, although his regiment was unsupported and the Union garrison was able to form a line of battle.[3] Collins' Battery soon began firing at the Union position, and the defenders fled in panic.[22] Initially, the Confederates were unaware that the defenders had fled, as they had left their flags flying above the fortifications.[3] After the fighting ended, Thompson's men looted Sedalia, with government property being particular targets for destruction,[25] although a modern historian states that Thompson attempted to limit the plundering to military-related supplies.[23] However, some eyewitnesses reported seeing Confederates plundering supplies of whiskey by riding barefoot and keeping the liquor in their boots.[25] Most of the Confederate units that had participated in the fighting became disorganized, and Slayback's Battalion, which was in the best state of organization,[3] performed guard duty after the battle.[26]

Price's Missouri Raid in October 1864

Price reported capturing a number of weapons and some military goods, as well as 200 prisoners.[21] The Union garrison is also reported to have suffered one man killed and 23 wounded.[24] Thompson then moved north to rejoin Price's main body, as it moved towards Marshall.[21] Clark's raid on Glasgow was also successful. By October 19, the Confederates had reached Lexington, where they fought against a Union force in the Second Battle of Lexington. Two days later, Union Major General James G. Blunt attempted to stop Price at the crossing of the Little Blue River, but was defeated in the ensuing Battle of Little Blue River. After fighting several more actions, Price encountered nearly 20,000 Union soldiers near Kansas City on October 23. The Battle of Westport followed, and Price's 9,000 soldiers were soundly defeated.[27] Price then fell back into Kansas but was defeated in the Battle of Mine Creek on October 25. About 600 Confederate soldiers were captured at Mine Creek, including Marmaduke. Later that day, Price ordered the destruction of almost all of the cumbersome wagon train.[28] The final major action of the campaign occurred on October 28 near Newtonia, Missouri. In the Second Battle of Newtonia Price was defeated by Blunt; by this point, the Confederate army was disintegrating. Union troops continued pursuing Price until the Confederates reached the Arkansas River on November 8; the Confederates did not stop retreating until they reached Texas[29] towards the end of the month.[30]