The Battle of Wilson's Creek, also known as the Battle of Oak Hills, is the first major battle of the Trans-Mississippi Theater of the American Civil War.

Fought on August 10, 1861, near Springfield, Missouri, between Federal forces and the Missouri State Guard, it is sometimes called the "Bull Run of the West."

At the beginning of the war, Missouri maintains an officially neutral status.

However, its governor, Claiborne Fox Jackson, has begun to work to bring Missouri out of the Union by purchasing arms from and fighting alongside Confederate troops.

The two sides repeatedly skirmish, most notably in the Camp Jackson affair, the Battle of Boonville, and the Battle of Carthage.

Jackson's support for secession results in his removal by a constitutional convention in July.

Jackson refuses to accept the maneuver as valid, and continues to act as governor.

In early August 1861, Confederates under the command of Brig. Gen. Benjamin McCulloch and Missouri State Guard troops under the command of Maj. Gen. Sterling Price approach Union Brig. Gen. Nathaniel Lyon's Army of the West, which is camped at Springfield.

On August 9, both sides formulate plans to attack the other.

At about 5:00 a.m. on August 10, Lyon, in two columns commanded by himself and Col. Franz Sigel, attack the Confederates on Wilson's Creek about twelve miles (nineteen kilometers) southwest of Springfield.

Confederate cavalry receive the first blow and retreat from the high ground, later referred to as "Bloody Hill," and infantry soon rush up to stabilize their positions.

The Confederates attack  the Union forces three times during the day, but fail to break through.

When Lyon is killed during the battle and General Thomas William Sweeny wounded, Major Samuel D. Sturgis assumed command of the Union forces.

Meanwhile, the Confederates rout Sigel's column south of Skegg's Branch.

Following the third Confederate attack, which ends at 11:00 a.m., the Union withdraws.

When Sturgis realizes that his men are exhausted and lacking ammunition, he orders a retreat to Springfield.

The Confederates are too disorganized and ill-equipped to pursue the retreating Federal forces.

The Confederate victory buoya Southern sympathizers in Missouri and servea as a springboard for a bold thrust north that carriea Sterling Price and his Missouri State Guard as far as Lexington.

In late October, a convention organized by Jackson meets in Neosho and passea out an ordinance of secession.

Although the state will reamain in the Union for the remainder of the war, the Battle of Wilson's Creek effectively gives the Confederates control of southwestern Missouri.

Today, the National Park Service operates Wilson's Creek National Battlefield on the site of the original conflict.