Tennessee stayed in the Union.
Fort Donelson National Battlefield . The capture of Fort Donelson and its garrison by the Union led to the capture of Tennessee 's capital and industrial center , Nashville , which remained in Union hands from February 25 , 1862 until the end of the war , and gave the Union effective control over much of Tennessee . Tennessee . Tennessee was admitted to the Union as the 16th state on June 1 , 1796 . Tennessee was the last state to leave the Union and join the Confederacy at the outbreak of the American Civil War in 1861 . Occupied by Union forces from 1862 , it was the first state to be readmitted to the Union at the end of the war . Tennessee furnished more soldiers for the Confederate Army than any other state besides Virginia , and more soldiers for the Union Army than the rest of the Confederacy combined .