To ensure that the civil rights act of 1866 would not be overturned, congress proposed the amendment, which would grant citizenship to african americans.

The correct answer is the 14th amendment.

The 14th amendment states that all citizens born or naturalized in the US are guaranteed the liberties/freedoms provided by the US Constitution. The goal of this amendment was to ensure that newly freed slaves had the same rights as white citizens. Even though this was supposed to help, Southern law makers still found ways around this amendment by implementing poll taxes and literacy tests to prevent African-Americans from voting.