Why did southerners object to Hamilton’s plan to pay off America’s war debt

Hamilton believed this was necessary to establish the United States' credit and promote investment. ... Northern members supported it because their debts were largely unpaid but Southern members, including Madison, opposed it because southern states had paid off a significant portion of their debt.

regarding the law, the 15th amendment was specifically designed thinking in the rights of black free men.

even though ratified on february 3, 1870, the promise of the 15th amendment would not be fully applied for a long time.poll taxes and literacy tests would allow southern states disenfranchise african americans. only in 1965 the voting rights for african americans would be actually able to vote in the south.

in 1965, president johnson signed the voting rights act, which aimed to overcome legal barriers that prevented african americans from voting as it was guaranteed by the 15th amendment to the u.s. constitution.