GEOLOGY OF THE WAR OF 1812: TERRAIN INFLUENCES ON THE BATTLE OF THE SINK HOLE, MISSOURI TERRITORY

In the western theater during the War of 1812, territorial militias such as the Missouri Rangers, as well as U.S. Army Regulars and settlers, fought British allies, the Sauk and Fox tribes of northern Illinois. The latter sought to limit westward expansion of the United States and form independent Native American states. Sauk and Fox war parties conducted hit-and-run guerilla style tactics, where geology and terrain played a pivotal role in determining outcomes of small-scale engagements. American forces were largely defensive and relied on topography and water resources to determine fort locations.

The Battle of the Sink Hole in Lincoln County is credited with being the last engagement of the war; an estimated force of 30 to 50 Sauk and Fox, under Chief Black Hawk, attacked a group of men from the fort on May 24, 1815 near Fort Howard on the western edge of the Mississippi River valley, approximately 55 km northwest of St. Louis, Missouri. A group of approximately 50 Missouri Rangers and Regulars, under the command of Capt. Peter Craig, immediately engaged the Sauk and Fox about 300 m south of Fort Howard. Within a few minutes, a detachment of 20 soldiers from Cape au Gris, under Capt. David Musick, joined the fight from the Cuivre River, which is 3 km south of the engagement. Sauk and Fox forces divided; some escaped north to Bob’s Creek, while Black Hawk and approximately 20-35 braves took cover in a sinkhole. American forces partly surrounded the sinkhole, pinning Black Hawk’s force. The sinkhole karst terrain provided excellent natural cover for defensive positions; despite superior American forces, the Native American position was not overrun. Both forces withdrew at dusk; the engagement was indecisive.

Historical first-hand accounts provide strong evidence for the location of the battlefield. A karst plain on the highlands overlooking the Mississippi River has numerous sinkholes in the lower St. Louis Limestone (Mississippian–Meramecian). The St. Louis Limestone is approximately 30 m thick, and the lower part contains pink chert clasts overlain by peritidal carbonates and solution-collapse breccias. Fort Howard was located adjacent to Cave Spring at the edge of the river valley. The cave and spring emanate from the base of the St. Louis Limestone, where the upper shaly beds of the Salem Limestone form a confining layer.