The site was established to preserve the area of the American Civil War battle that took place in October 28–29, 1862 between Union forces and Confederate guerrillas.

[4][5] A correspondent of The New York Times reported on the battle; the headline noted the "desperate bravery" of the African Americans in achieving Union victory.

[7] It encompasses much of the Toothman homestead, which was commandeered by the Union troops, fortified with temporary breastworks and christened "Fort Africa."

[9] During the Battle of Island Mound (aka "Battle of Fort Toothman" or "Fort Africa") on October 28–29, 1862, the Union 1st Kansas Colored Volunteers—composed of former Arkansas and Missouri slaves—and a scouting team of Cherokee and blacks from the 5th Kansas Volunteer Cavalry engaged a numerically superior force of Confederate guerrillas and recent Missouri State Guard recruits led by Vard Cockrell and Bill Truman (who was related to future President Harry S. Truman).

The Union forces had crossed into Missouri on a mission to clear Confederate guerrillas from their base known as "Hog Island" in the Osage River.

[5] Finding themselves outnumbered in an early sortie, the Union troops commandeered and fortified the homestead of Confederate guerrilla Enoch John Toothman, and a one-day siege ensued.

Such positive reports provided encouragement to other African-American units that were forming across the northern states and petitioning the Union government to fight in combat.