The state of Texas seceded from the United States on February 1, 1861, and joined the Confederate States of America on March 2, 1861, replacing its governor, Sam Houston. During the subsequent American Civil War, Texas was most useful for supplying soldiers for Confederate forces and in the cavalry. Texas was mainly a "supply state" for the Confederate forces until mid-1863, when the Union capture of the Mississippi River made large movements of men, horses or cattle impossible. Some cotton was sold in Mexico, but most of the crop became useless because of the Federal naval blockade of Galveston and other ports.