The Confederate states rejoined the United States from 1866 through 1870, during the period of Reconstruction. The first state to be readmitted was Tennessee in 1866, while the rest of the South was broken up into five regions before their readmittance.
In 1868, Alabama, Arkansas, Florida, Georgia, Louisiana, North Carolina and South Carolina were readmitted to the Union. Georgia, however, promptly forced all the black Americans out of their state legislature, which forced the U.S. Government to reinstate martial law. It was once again admitted back into the Union in 1870 along with the final former Confederate states of Texas, Virginia and Mississippi.