The Missouri State Guard (MSG) was a military force established by the Missouri General Assembly on May 11, 1861. While not a formation of the Confederate States Army, the Missouri State Guard fought alongside Confederate troops and, at various times, served under Confederate officers.

The Battle of Wilson's Creek, also known as the Battle of Oak Hills, was the first major battle of the Trans-Mississippi Theater of the American Civil War. It was fought on August 10, 1861, near Springfield, Missouri.