Arkansas's secession in May of 1861 was not unanimous. The state's wealth had always been concentrated in the hands of relatively few men who owned cotton plantations and slaves. These men and their families were not full-time Arkansas residents, either. Most owned several plantations in states throughout the South, and saw Arkansas —especially Southwest Arkansas — simply as an outpost to their vast holdings. They nonetheless held the power in the state and federal legislatures, even going so far as prohibiting free blacks from living in Arkansas at all.
The people in Southwestern Arkansas in particular were much more populist and had a strong free-soil expansionist base before the Civil War. Its newspaper editors and local politicians (such as Augustus Hill Garland) were Whigs or Unionist Democrats. For a long time, this portion of the state was also an international boundary between the U.S. and Spain/Mexico/Texas, and therefore leaned towards a more industrialized economy that relied on free, not slave labor. Locals even pushed for a transcontinental railroad route through Fulton. Their economic and political interests tended to mirror the Arkansans in the northwestern region, who relied on coal mining, not cotton farming.
The vote for secession was therefore very contentious, and secessionists, fearing that Unionists would win a popular vote, confined the vote to the legislature only. So while the state did secede, it seems that the men who fought for Arkansas during the Civil War did so to protect their fellow inhabitants, and not for any philosophical difference in the United States.
In September of 1863, the capitol of Arkansas fell into Union hands relatively easily. While the Confederates simply moved their archives to Washington, the damage was done - the U.S. considered Arkansas to be back under federal control. This led to the belief that the southern part of the state would be the staging area for the run-up to the Red River Campaign in Louisiana, led by Nathaniel Banks. In March of 1864, Union troops under the command of Frederick Steele were ordered to move south from Little Rock, Arkansas into the Confederate-controlled Ouachita River Valley.
The Confederates refused to allow Steele's men any passage. They stopped advancement at Elkin's Ferry along the Little Missouri River north of Washington as the Union marched southward to Washington in Hempstead County. To avoid disruption in the state government, citizens removed the state archives further west to little Rondeau (Rondo) in Miller County. Confederates also destroyed roads, bridges, and ferries to halt Union movement, and built a dirt fortification around Dooley's Ferry on the Red River to prevent Union access. Due to the destruction and Confederate maneuvers, Steele could not obtain adequate supplies for his troops. In April 1864, Steele attempted to seize the supply depots at Camden. The Confederates built Fort Southerland and Fort Lookout around Camden to defend the town from the attack.
The main objective of the Confederates, led by Sterling Price, was to defend Washington. To get Price away from the Washington and Camden road in order to take Camden, Steele and his troops engaged Price and his troops, among them Choctaw regiments led by Texans Maxey and Gano, at Prairie d'Ane in Nevada County (near Prescott) in early April, 1864. The battle lasted several days, and included a night battle. The Union army, which substantially outnumbered the Confederates, included a Unionist Arkansas infantry. Steele's army gained control of Camden. However, there weren't many provisions in Camden, forcing him to look to look elsewhere.
Price continued to patrol the area to keep Washington out of Union hands. Steele, while occupying Camden, searched for supplies throughout the region. Confederate forces engaged Union supply trains at Poison Spring (Ouachita County) and Marks' Mills (Cleveland County). Many of these battles were considered "skirmishes" as they consisted of surprise ambushes and left bloody messes in their wake without much of a resolution. Steele had no choice but to render the Camden Campaign a failure, and dealt with one final, bloody battle at Jenkin's Ferry (Grant County) before bringing his troops back to Little Rock. Ultimately, the result was that the Red River Campaign in Louisiana would not gain the reinforcements it needed to invade Texas.