President Lincoln pushed for strong laws to help the 4 million former slaves. Congress passed, and the states ratified, the Thirteenth, Fourteenth, and Fifteenth Amendments to the Constitution.
The Thirteenth Amendment, passed in 1865, stated that enslavement of any group of people was forever unlawful.
The Fourteenth Amendment, passed in 1866, stated that every person born in the United States was a citizen of the United States and the state in which they reside.
The Fifteenth Amendment, passed in 1870, stated that the right to vote shall not be denied because of race or the fact that a person was a former slave.
Remember, only men were allowed to vote in the United States when these amendments were passed; women were not allowed to vote.