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 formed the pro-secession
Missouri State Guard, a
militia unit.
Brigadier General Nathaniel Lyon of the
Union Army evicted Jackson and the pro-secession portion of the
state legislature from the state capital of
Jefferson City. The Missouri State Guard won several battles, but Union forces had the secessionists restricted to the southwestern portion of the state by the end of the year. Jackson and the secessionists formed the
Confederate government of Missouri, which would function as a
government-in-exile for much of its existence, moving from place to place before settling in
Marshall, Texas; Missouri now had two competing governments. The Union gained control of Missouri in March 1862 after the
Battle of Pea Ridge, and the state was then plagued by
guerrilla warfare throughout 1862 and 1863.
Price's Raid By the beginning of September 1864, events east of the
Mississippi River, 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 a war-ending armistice that would preserve slavery. 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 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.
Major General Sterling 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 was a former governor of Missouri, had served in the
Mexican-American War, and had commanded the
Missouri State Guard in 1861 before entering Confederate service. Price expected that the campaign 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 as the state's primary defensive force), and aid McClellan's chance of defeating Lincoln. On September 19, Price's column of about 12,000 to 13,000 men entered the state. Price soon learned that a Union force held
Fort Davidson near
Pilot Knob. Not wanting to leave a large Union force in the rear of his army, Price decided to attack the Union post. The attack, known as the
Battle of Fort Davidson, occurred on September 27, and the Confederates were repulsed with heavy losses. While the fort's defenders retreated that night, Price decided to abandon plans to capture
St. Louis as his troops had suffered at least 800 casualties and their morale had been dented. After giving up the proposed St. Louis thrust, Price's army headed for Jefferson City, although the Confederates were slowed by bringing along a large
supply train. On October 7, the Confederates approached Jefferson City, which was held by about 7,000 men, mostly inexperienced militia. Faulty Confederate intelligence placed Union strength at 15,000, and Price, fearing another defeat like Fort Davidson, decided not to attack the city, and began moving his army towards Boonville the next day. Boonville was in the pro-Confederate region of
Little Dixie in central Missouri, and according to different sources Price was able to recruit around either 1,200 or 2,500 men. Price, needing weapons and supplies, then authorized two raids away from his main body of troops: Brigadier General
John B. Clark Jr. was sent to
Glasgow, and Missouri State Guard Brigadier General
M. Jeff Thompson's
brigade of Brigadier General
Joseph O. Shelby's division to
Sedalia. ==Battle==