Final answer:
Georgia reentered the Union in 1870 after meeting requirements including military intervention, seating of black legislators, and ratification of the Fifteenth Amendment. However, Democratic gains in 1871 marginalized the progress made by freedpeople.
Step-by-step explanation:
Georgia was the last of the unreconstructed states to be readmitted to the Union. This happened after a series of events during President Ulysses S. Grant's administration, which included a return to military rule in December 1869 to remedy issues in the state legislature.
Georgia finally reentered the Union in 1870, following the requirements that were set forth, which included the seating of black legislators and the ratification of the Fifteenth Amendment, extending full political rights to blacks. However, this progress was short-lived as the Democrats regained power in the state in 1871, undermining the gains made by freedpeople.
The question is asking about the year when Georgia finally got back into the Union during the period of Reconstruction. In 1870, the Republicans, with the military's support, ousted the conservative ex-Confederates, seated the black legislators, ratified the Fifteenth Amendment, and returned the state to the Union.
However, the Republican gains in Georgia did not last long. In 1871, the Democrats won control of the state legislature and the governor's office and slowly chipped away at the gains the freedpeople made.