What happened at the battle of Wilson's Creek?

The Battle of Wilson's Creek was between secessionists in the Missouri State Guard and Union forces under Brigadier General Nathaniel Lyon, on August 10, 1861. The union forces attacked but were outmaneuvered, and Lyon was killed. The Confederate forces failed to defeat the Union forces, but compelled them to withdraw. The Union retreat meant Confederate sympathizers controlled southern Missouri, and did so throughout much of the the Civil War.

It was not until October, 1864, that Missouri was captured by the Union Army of the Border, whose manpower outnumbered the South by three-to-one.