The Kansas-Nebraska Act

 

This 1856 map shows slave states (gray), free states (pink),
U.S. territories (green), and Kansas in center (white).

In January 1854, Senator Stephen A. Douglas introduced a bill that
divided the land west of Missouri into two territories, Kansas and
Nebraska. He argued for popular sovereignty, which would allow the
settlers of the new territories to decide if slavery would be legal
there. Douglas hoped that the formula for popular sovereignty would
ease national tensions over the issue of human bondage and that he
would not have to take a side on the issue. Anti-slavery supporters
were outraged because, under the new terms of the Missouri Compromise
of 1820, slavery would have been outlawed in both territories. After
months of debate, the Kansas-Nebraska Act passed on May 30, 1854.
Pro-slavery and anti-slavery settlers rushed to Kansas, each side
hoping to determine the results for the first election held after the
new law went into effect. The conflict turned violent, aggravating the
split between the North and South until reconciliation was virtually
impossible. This led to Bleeding Kansas. Opponents of the
Kansas-Nebraska Act helped found the Republican Party, which opposed
the spread of slavery into the territories. As a result of the
Kansas-Nebraska Act, the United States moved closer to Civil War.