Texas declared its secession from the Union on February 1, 1861, and joined the Confederate States on March 2, 1861, after it had replaced its governor, Sam Houston, who had refused to take an oath of allegiance to the Confederacy. As with those of other states, the Declaration of Secession was not recognized by the US government at Washington, DC. Some Texan military units fought in the Civil War east of the Mississippi River, but Texas was more useful for supplying soldiers and horses for the Confederate Army. Texas' supply role lasted until mid-1863, when Union gunboats started to control the Mississippi River, which prevented large transfers of men, horses, or cattle. Some cotton was sold in Mexico, but most of the crop became useless because of the Union's naval blockade of Galveston, Houston, and other ports.

The Confederate States of America (CSA), commonly referred to as the Confederate States (C.S.), the Confederacy, or the South, was an unrecognized breakaway republic in the Southern United States that existed from February 8, 1861, to May 9, 1865. The Confederacy comprised eleven U.S. states that declared secession and warred against the United States during the American Civil War. The states were South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, Texas, Virginia, Arkansas, Tennessee, and North Carolina.