History: American Civil War (1861-1865)

Trans-Mississippi theater 1861–1865
Guerrilla activity turned much of Missouri into a battleground. Missouri had, in total, the third-most battles of any state during the war. The other states of the west, though geographically isolated from the battles to the east, saw numerous small-scale military actions. Battles in the region served to secure Missouri, Indian Territory, and New Mexico Territory for the Union. Confederate incursions into New Mexico territory were repulsed in 1862 and a Union campaign to secure Indian Territory succeeded in 1863. Late in the war, the Union's Red River Campaign was a failure. Texas remained in Confederate hands throughout the war, but was cut off from the rest of the Confederacy after the capture of Vicksburg in 1863 gave the Union control of the Mississippi River.