Tennessee was the last state to leave the Union.
Georgia (U.S. state) . It was the last state to be restored to the Union , on July 15 , 1870 . 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 .