Dred Scott v. Sandford (1857) 
Dred Scott was taken by his master, John Sandford, from the slave state of Missouri to Illinois (a free state by the Missouri Compromise of 1820) with his master. Upon his return to Missouri , Scott sued on the grounds that he was not a slave due to the time he had spent in freedom.   The US Supreme Court held by 7-2 that no one but a citizen of the United States could be a citizen of a state, and that only Congress could confer national citizenship.  Chief Justice Roger Taney, from a slave owning family in Maryland , concluded that the phrase “all men are created equal” from the Declaration of Independence was never meant to apply to the enslaved African race and that no person descended from an African slave could be a citizen. The ruling also held that Missouri Compromise – which prohibited slavery north of the 36^th parallel in the land of the Louisiana Purchase – was unconstitutional. 

http://www.oyez.org/cases/1851-1900/1856/1856_0/