"Under the terms of the Reconstruction Acts, new state constitutions were written in the South. By Aug., 1868, six states (Arkansas, North Carolina, South Carolina, Louisiana, Alabama, and Florida) had been readmitted to the Union, having ratified the Fourteenth Amendment as required by the first Reconstruction Act. The four remaining unreconstructed states—Virginia, Mississippi, Texas, and Georgia—were readmitted in 1870 after ratifying the Fourteenth Amendment as well as the Fifteenth Amendment, which guaranteed the black man's right to vote."

From: http://encyclopedia2.thefreedictionary.com/Readmission+of+states

The site goes into greater detail, but the above paragraph answers your question pretty well. Stan