Answer:
A free African-American was a citizen of the US.
Explanation:
Scott v. Sanford, or Dred Scott v. Sanford, was a case heard by the Supreme Court in 1857, when America still practiced slavery. A slave that had escaped to a free state, Dred Scott, was re-captured and taken back to the South. He then sued the slaveowners, and the case made it to the Supreme Court. Unfortunately, the Court decided that slaves, even if they're in a free state, do not have rights and are not citizens of the US.