Arkansas had become the 25th state of the United States, on June 15, 1836, entering as a slave state. Antebellum Arkansas was still a wilderness in most areas, rural and sparsely populated. As a result, it did not have early military significance when states began seceding from the Union.

During the secession crisis, but before Arkansas had seceded and before the onset of any fighting, the Federal Arsenal in Little Rock became a potential flash point. The small Federal garrison was forced to evacuate after a demand by Arkansas Governor Rector that the arsenal be turned over to state authority.

At the beginning of 1861, the population of Arkansas, like several states of the Upper South, was not keen to secede on average, but they were also opposed to Federal coercion of seceded states. This was shown by the results of state convention referendum in February 1861. The referendum passed, but the majority of the delegates elected were conditional unionist in sympathy, rather than outright secessionst. This changed after the Confederacy attacked Fort Sumter in South Carolina, and Abraham Lincoln called for troops to put down the rebellion. The move toward open war shifted public opinion into the secessionist camp, and Arkansas seceded from the Union on May 6, 1861. Despite its relative lack of strategic importance, the state was the scene of numerous small-scale battles during the Civil War.

Arkansans of note during the Civil War include Confederate Major General Patrick Cleburne. Considered by many to be one of the most brilliant Confederate division commanders of the war, Cleburne is often referred to as "The Stonewall of the West." Also of note is Maj. Gen. Thomas C. Hindman, a former United States Representative, who commanded Confederate forces at the Battle of Cane Hill and Battle of Prairie Grove. Brigadier General Albert Rust, through his political influence, helped to form the 3rd Arkansas Infantry Regiment, and until his promotion to general commanded that regiment. He later commanded forces at the Battle of Pea Ridge and the Battle of Shiloh, ultimately serving under General Sterling Price. Colonel Van H. Manning took over command of the 3rd Arkansas following Rust's promotion, and was commended for bravery in several engagements, most notably at the Devil's Den during the Battle of Gettysburg.

Due to Arkansas having no real strategic inportance, short of being a gateway into Texas, few major battles were fought there. The Camden Expedition (March 23 – May 2, 1864) was the most important military campaign in Arkansas. Maj. Gen. Frederick Steele and his Union troops stationed at Little Rock and Fort Smith were ordered to march to Shreveport, Louisiana. There, Steele was supposed to link up with a separate Federal amphibious expedition which was advancing up the Red River Valley. The combined Union force was then to strike into Texas. But the two pincers never converged, and Steele's columns suffered terrible losses in a series of battles with Confederates led by Maj. Gen. Sterling Price and Gen. Edmund Kirby Smith.

When the Emancipation Proclamation went into effect on January 1, 1863, Union forces were in occupation of northwestern Arkansas. Local Union commanders, who had been aggressively enforcing the Confiscation Acts to grant freedom to slaves of rebel owners, put the proclamation into effect immediately, freeing many slaves in the area.[1]

The Fort Smith Council was a series of important meetings held at Fort Smith in September 1865 that were organized by the United States government for all Indian tribes east of the Rockies. The purpose was to discuss the future treaties and land allocations following the close of the Civil War. Under the Military Reconstruction Act, Congress readmitted Arkansas in June 1868.