Wilson's Creek National Battlefield - http://www.nps.gov/wicr
The battle fought here on August 10, 1861, was the first major Civil War engagement west of the Mississippi River, involving about 5,400 Union troops and 12,000 Confederates. Although a Confederate victory, the Southerners failed to capitalize on their success. The battle led to greater federal military activity in Missouri, and set the stage for the Battle of Pea Ridge in March 1862. Wilson's Creek was also the scene of the death of Nathaniel Lyon, the first Union general to be killed in combat. With the exception of the vegetation, the 1,750 acre battlefield has changed little from its historic setting, enabling the visitor to experience the battlefield in near pristine condition.