As a result of the long campaign, siege, and surrender in July 1863 by Gen. John C. Pemberton, the Union gained control of the entire Mississippi River, splitting the Confederacy.
In the 1864 Red River Campaign, a U.S. force under Major General Nathaniel P. Banks tried to gain control over northwestern Louisiana, but was thwarted by Confederate troops commanded by Richard Taylor.
Attempts to press further northward in the territory were unsuccessful, and Confederate forces withdrew from Arizona completely in 1862 when Union reinforcements arrived from California.
Arkansas Though a slave state with a highly organized and militant secessionist movement, thanks to the pro-slavery "border ruffians" who battled antislavery militias in Kansas in the 1850s, Missourians sided with the Union by a ratio of two or three to one.
Gangs of Confederate insurgents, commonly known as "bushwhackers", ambushed and battled Union troops and Unionist state militia forces.
Historians have offered various explanations for the anomalously high level of guerrilla activity in Missouri, including the possibility that the violence was linked to thousands of court-ordered sales of property belonging to the state's Confederate sympathizers, beginning in 1862 and continuing throughout the war.
The property sales arose from court judgments for defaulted debts incurred early in the war to arm rebel troops.
Referred to as the "back door" of the Confederacy, Texas and western Louisiana continued to provide cotton crops that were transferred overland to the Mexican border towns of Matamoros and the port of Bagdad, and shipped to Europe by means of blockade runners in exchange for supplies.
Confederate victories at Galveston, Texas, the Battle of Sabine Pass and the Second Bayou Teche Campaign repulsed invasion forces.
[3] Isolated from events in the east, the Civil War continued at a low level in the trans-Mississippi theater for several months after Lee's surrender in April 1865.
A campaign led by Union General James G. Blunt to secure Indian Territory culminated with the Battle of Honey Springs on July 17, 1863.
[5] Officers and soldiers supplied to the Confederacy from Native American lands numbered at 7,860[5] and came largely from the Cherokee, Chickasaw, Choctaw, Creek, and Seminole nations.
[7] The Confederate States Army's Trans-Mississippi Department was formed May 26, 1862, to include Missouri, Arkansas, Texas, Indian Territory (now Oklahoma), and Louisiana west of the Mississippi River.
It absorbed the previous Trans-Mississippi District (Department Number Two), which had been organized January 10, 1862, to include that part of Louisiana north of the Red River, the Indian Territory (later State of Oklahoma, 1907), and the states of Missouri and Arkansas, except for the country east of St. Francis County, Arkansas, to Scott County, Missouri.