From The Fiery Trial: Abraham Lincoln and American Slavery, by Eric Foner, chapter 4.
Two days after the inauguration of James Buchanan in March 1957, the Supreme Court handed down one of the most infamous decisions in its history. During the 1830s, Dred Scott, a slave of Dr. John Emerson of Missouri, resided with his owner in Illinois, where state law prohibited slavery, and the Wisconsin territory, from which it had been barred by the Missouri Compromise. He married another slave, Harriet Scott, and in 1846, after returning to Missouri, the Scott family, by now consisting of husband, wife, and two daughters, went to court claiming that residence on free soil had made them free. In time, the case made its way to the Supreme Court. Chief Justice Roger B. Taney, supported by sic other members of the court, concluded that the Scotts must remain slaves. No black person, Taney declared, could be a citizen of the United states and thus the Scotts had no standing to sue in court. The case could have ended there. Taney, however, went on to argue that because the Constitution “distinctly and expressly affirmed” the right to property in slaves, slaveholders could bring them into federal territories. The Missouri Compromise– repealed three years earlier by the Kansas-Nebraska Act– had therefore been unconstitutional. Only once before, in the landmark case of Marbury v. Madison, which established the principle of judicial review, had the Court invalidated an act of Congress on constitutional grounds.
Much of Taney’s opinion consisted of a historical discussion purporting to demonstrate that the founding fathers had not recognized black persons as part of the American people. The framers of the Constitution, he insisted, regarded blacks, slave and free, as “beings of an inferior order, and altogether unfit to associate with the white race.. and so far inferior, that they had no rights that the white man was bound to respect.” (This statement, Thaddeus Stevens later remarked, “damned [Taney] to everlasting fame; and, I fear, everlasting fire.”) States could make free blacks citizens if they wished, but this did not require the federal government or other states to recognize them as such. No state could unilaterally “introduce a new member into the political community created by the Constitution”– a community, according to Taney, limited to white persons.
“The most important decision ever made by the Supreme Court,” as the New York Times described it, Dred Scott was the work of a chief justice who belonged to a long-established planter family in Maryland. Taney had manumitted his own slaves in the 1820s but strongly believed in black inferiority. He seems to have thought that the Supreme Court could restore sectional harmony by resolving the slavery controversy. The decision had precisely the opposite effect. As a Georgia newspaper exulted, it “covers every question regarding slavery and settles it in favor of the South.” Taney had declared unconstitutional the platform of the nation’s second largest political party. His ruling also seemed to undercut Stephen A. Douglas’s popular sovereignty doctrine, for if Congress lacked the authority to deprive slaveholders of their constitutionally guaranteed right to bring slaves into a territory, how could a territorial legislature created by Congress do so?
…The Dred Scott decision propelled to the forefront of public debate questions that would dominate politics until the outbreak of the Civil War: the founders’ intentions regarding slavery; whether slavery should be viewed as a local or national institution; and the constitutional authority of the federal government to prohibit slavery in the territories. Lincoln had already expressed his opinion on these issues and would continue to do so between 1857 and 1860. But the decision inspired him to elaborate his views on a subject about which he had previously said very little, the place of blacks in American society. Lincoln knew that this question carried an explosive political charge. Soon after the Court issued its ruling, Stephen A Douglas delivered impassioned speeches declaring that the Declaration of Independence and Constitution had been written for whites and charging that Republicans who opposed the Dred Scott decision favored “perfect and absolute equality of the races.” Lincoln believed that rhetoric of this kind had played a role in Fremont’s defeat in the presidential election of the previous November. Republicans, Lincoln wrote, had been “constantly charged with seeking an amalgamation of the white and black races; and thousands turned from us… fearing to face it themselves.” If others would not “face it,” he would.
Lincoln later called Dred Scott a “burlesque upon judicial decisions.” On June 26, 1857, two weeks after Douglas spoke in Springfield in its support, Lincoln responded in the same city. The decision, he argued, was so erroneous that it could not be viewed as having established a “settled doctrine for the country.” Nearly all Republican leaders agreed. But unlike most Republicans politicians, who preferred to attack Taney for having taken on the territorial question when he need not have done so and who devoted most of their attention to the constitutional power of Congress to bar the institution in the territories, Lincoln addressed head-on the vexatious question of black citizenship. He denied that Taney had presented a plausible account of the founders’ racial outlook. Free blacks, he pointed out, echoing Justice McLean’s dissent, had voted in several states at the time the Constitution was ratified, indicating that they were them viewed as members of the body politic. Taney, moreover, was “grossly incorrect” to imply that “the public estimate of the negro” had improved since the revolutionary era; in fact, “the change between then and now is decidedly the other way.” Lincoln conspicuously failed to mention the deteriorating situation in Illinois, whose voters and legislature within the past decade had approved measures barring free blacks from entering the state….
More information on Dred Scott from PBS here: http://www.pbs.org/wgbh/aia/part4/4p2932.html