Final answer:
The Southern states could seek readmission into the Union after meeting Reconstruction requirements, which included holding state conventions, repealing secession ordinances, and ratifying the Thirteenth and Fifteenth Amendments.
Step-by-step explanation:
After Southern states did all the things they were required to do to be considered reconstructed, they could seek readmission into the Union. The requirements for readmission were to hold state conventions, repeal ordinances of secession, and ratify the Thirteenth and Fifteenth Amendments.
The Thirteenth Amendment abolished slavery, and the Fifteenth Amendment specified that the right to vote could not be denied on account of race, color, or previous condition of servitude. While President Andrew Johnson declared the Union restored as early as 1866, Radical Republicans in Congress did not agree with his lenient stance and only allowed states back into the Union once they met the criteria established by Congress.
By the summer of 1868, several states had been readmitted, and by 1870 all remaining Confederate states were reintegrated into the Union after meeting the conditions set forth, marking the end of Reconstruction.