So Lincoln's Emancipation Proclamation didn't technically free anybody. Lincoln knew this, and he worked toward getting constitutional amendments passed to abolish slavery and guarantee citizenship for blacks. The amendments he pushed for were passed after his death, but were mostly hollow attempts at black citizenship.
- The 13th Amendment (1865) abolished slavery but provided no citizenship for blacks.
- The 14th Amendment (1868) prohibited states from taking away citizens' rights without due process, but the Supreme Court decisions in the 1870s weakened blacks' rights. This amendment would remain weak until the 1960s, when it became the basis for the Civil Rights movement.
- The 15th Amendment (1870) prohibited discrimination of the right to vote based on race. In response, much of the South passed Black Codes (and later Jim Crow laws), which instituted poll taxes and literacy tests, excluding many former slaves. The black right to vote wouldn't truly be realized in the South until the Voting Rights Act of 1965.
After Lincoln's assassination came Andrew Johnson's administration and the rise of Radical Republicans, who wanted to punish the defeated South. Congress didn't trust Johnson -- or his promotion of Lincoln's lenient policy of welcoming the South back into the Union.