Claiborne Jackson, the pro-Southern Governor of Missouri, wanted the state to secede and join the Confederacy.
Union Brigadier General Nathaniel Lyon set out to put down Jackson's Missouri State Guard, commanded by Sterling Price.
Reaching Jefferson City, the state capital, Lyon discovered that Jackson and Price had retreated towards Boonville.
Lyon reembarked on steamboats, transported his men to below Boonville, marched to the town, and engaged the enemy. In a short fight, Lyon dispersed the Confederates, commanded on the field by Colonel John S. Marmaduke, and occupied Boonville.
This early victory established Union control of the Missouri River and helped douse attempts to place Missouri in the Confederacy.
Result(s): Union victory
Location: Cooper County
Campaign: Operations to Control Missouri (1861)
Date(s): June 17, 1861
Principal Commanders: Brigadier General Nathaniel Lyon [US]; Colonel John S. Marmaduke [CS]
Forces Engaged: Combined force of Missouri troops and Regular U.S. Army (approx. 1,700) [US]; State Guard Troops [CS]
Estimated Casualties: 81 total (US 31; CS 50)