After the Revolutionary War, the Northwest Territory was formed in 1787. Several Midwestern states were formed from the territory: Ohio, Indiana, Illinois, Michigan, Wisconsin and Minnesota. Inevitably, encroachment by Americans into Indian lands led to warfare. The Battle of Fallen Timbers , St. Clair's Defeat/Battle of the Wabash , The Battle of Tippecanoe  and Black Hawk's War  were among the notable battles waged in the "Old Northwest" before the native tribes were finally pushed west.
Check internet sites and pensions for information on soldiers [regular army and militia] who fought in these conflicts.