In August, Confederates under Brigadier General Benjamin McCulloch and Missouri State Guard troops under Maj. Gen. Sterling Price approached Brig.

On August 10, Lyon, in two columns commanded by himself and Col. Franz Sigel, attacked the Confederates on Wilson's Creek about 10 miles (16 km) southwest of Springfield.

When Lyon was killed and General Thomas William Sweeny wounded, Major Samuel D. Sturgis assumed command of the Union forces.

Although the state remained in the Union for the remainder of the war, the battle effectively gave the Confederates control of southwestern Missouri.

At the beginning of the American Civil War, Missouri declared that it would be an "armed neutral" in the conflict, and not send materials or men to either side.

Governor Claiborne F. Jackson had called out the Missouri Volunteer Militia (MVM) to drill on the edge of St. Louis in Lindell Grove.

The governor had clandestinely obtained artillery from the Confederacy and smuggled the pieces into the militia encampment – referred to as "Camp Jackson".

[7] After complaints by Missouri Unionists, Harney was replaced by Lyon (who was promoted to brigadier general of volunteers), further undermining the fragile truce.

On June 12, Lyon and Jackson met at the St. Louis' Planter's House Hotel in a last attempt to avoid a resumption of fighting.

Price and McCulloch developed plans to attack Springfield, but Lyon marched out of the city on August 1 in an attempt to surprise the Southern forces.

[13] Price favored an immediate attack on Springfield but McCulloch, doubtful about the quality of the Missouri State Guard, preferred to remain in place.

[14] Outnumbered, Lyon planned to withdraw northeast to Rolla to reinforce and resupply, but not before launching a surprise attack on the Missourian camp to delay pursuit.

Sigel proposed striking McCullough in a pincer movement, which would split the already outnumbered Union force; he planned to lead 1,200 men in a flanking maneuver while the main body under Lyon struck from the north.

Lyon concurred, and in accord with Sigel's plan, the Union army marched out of Springfield on the rainy night of August 9, leaving about 1,000 men to protect supplies and cover the retreat.

Early Union hopes for a rout were dashed, however, when the artillery of the Pulaski Arkansas Battery unlimbered and checked the advance, which gave Price's infantry time and cover to organize lines on the south slope of the hill.

[14] Meanwhile, McCulloch rallied several Confederate units, including the 3rd Louisiana Infantry and the 3rd Division from the Missouri State Guard, to lead a counterattack.

Sigel's men mistook the 3rd Louisiana for the 1st Iowa Infantry (which also wore gray uniforms) and withheld their fire until the Confederates were nearly upon them.

Price wanted to start a pursuit of the Union force immediately, but McCulloch refused, worried about the quality of the Missouri State Guard and the length of his supply line back to Arkansas.

[25] Although Price enjoyed some Missouri victories, notably the siege and capture of Lexington, he did not have the popular support to remain in the field, eventually retreating to northwest Arkansas.

Nevertheless, Missouri suffered extensive guerrilla warfare between Unionists and pro-Confederate bushwhackers such as Quantrill's Raiders and Bloody Bill Anderson throughout the war.

[30] The National Park Service operates a visitor center featuring exhibits, a fiber optic map displaying the course of the battle, and a research library.