Black soldiers fought for the first time in the Civil War in The Battle of Island Mound, 29 October 1862.
According to signage in the viewing station at the Battle of Island Mound Historic Site: "During the fall of 1862, Bates County (Missouri) had become a haven for guerrillas and Confederate recruiters." And "one of their favorite haunts was a marshy tract on the Marais-des-Cygnes River southwest of Butler (Missouri)."
A Union Army unit -- the First Kansas Colored Volunteer Infantry Regiment, composed primarily of former slaves -- moved into the area in late October. They established a camp on the Toothman Farm, dubbed "Fort Africa," and there, on 29 October 1862, repelled an opposing force of mounted southern guerillas who are believed to have outnumbered by as much as 6-to-1.
Their victory -- and they praise they won in it from miliatary leadership on both sides of the conflict -- did much to dispell the belief that blacks could not or would not serve well as soldiers.
Over the course of its three-year history, the First Kansas Colored Volunteer Infantry fought in 16 battles as well as many skirmishes.
Wikipedia reports that the "regiment lost at least 344 men" while active, including "5 officers and 173 enlisted men [who] were killed or mortally wounded, [and] 1 officer and 165 enlisted men [who] died of disease. No other Kansas regiment lost more men than the 1st Kansas Volunteer Infantry (Colored)."
According to the Missouri Department of Natural Resources, which established and maintains it, the Battle of Island Mound Historic Site " is a partner site in Freedom’s Frontier National Heritage Area and the National Underground Railroad Network to Freedom, both operated by the National Park Service. The heritage area is a consortium of parks, sites and museums in eastern Kansas and western Missouri that interpret the community, regional, and national stories of the journey to freedom. The National Underground Railroad Network to Freedom is a national effort to coordinate education efforts about the Underground Railroad and its role in assisting enslaved individuals seeking freedom" ( https://mostateparks.com/park/battle-island-mound-state-historic-site ).