Chief Justice John Marshall's tenure finally came to an end, with his death on July 6, 1835. President Andrew Jackson appointed Roger Taney (pronounced TAH-nee) to succeed Marshall.
Taney served as a state and federal attorney general, and as the federal secretary of the treasury. He then had a 28-year tenure as chief justice. A very active public career over many years. But I would venture a guess that at least 99% of everything that has ever been written about Taney involves only one of his Supreme Court opinions.
That was the 1857 decision in the case of Dred Scott v. Sandford.
Dred Scott was an African American slave, owned by John Emerson, a Missouri physician. During Emerson's service in the Army, he brought Scott with him to the free state of Illinois, and to territory that would later be included in the state of Minnesota.
After Emerson died in 1843, Scott initiated a series of legal actions, seeking his freedom. That process finally culminated in a Supreme Court decision in 1857.
The Court found that Scott was not a "citizen" in the sense in which Article III of the Constitution allows citizens to sue in the federal courts. In the opinion of the Court's majority, that was true of all people of African ancestry, regardless of their status as enslaved or free.
In his opinion for the Court, Taney presented evidence that none of the states who were the original parties to the Constitution would have recognized African Americans as citizens at the time Article III was written. Basing his decision on that criterion is an example of the doctrine of Original Intent, that has been championed in recent years by Associate Justice Antonin Scalia. Of course, by Scalia's time, the 14th Amendment had specifically reversed that supposed original intent, so the doctrine would not lead Scalia to the same result that Taney reached.
(That's not to paint Scalia as a supporter of the Dred Scott decision. In his dissenting opinion in the Planned Parenthood v. Casey abortion case of 1992, Scalia called Dred Scott "an erroneous and widely opposed opinion".)
The Court's interpretation of "citizen" was bound to be controversial at that time when tensions over slavery were continuing to build, and would lead four years later to Civil War. But another part of the Court's decision was even more incendiary in that respect. They found parts of the Missouri Compromise of 1820 to be unconstitutional. That compromise was part of what had kept the lid in place on the boiling slavery controversy up to that time.
The Missouri Compromise allowed that slave state to enter the union, in exchange for the admission of free Maine, and a limitation on the extension of slavery to territories north and west of Missouri. Striking down that compromise struck a raw nerve in the 1850s political arena. Abraham Lincoln, and other politicians in the new Republican Party, were not abolitionists, per se, at that time. But they strongly opposed the extension of slavery into any new western states.
The notion that someone such as Dred Scott could be held as a slave in those territories, and that the legislative protection against the extension of slavery no longer applied, made the status quo less tenable, and moved the country closer to Civil War.