The Kansas-Nebraska Act was passed by the U.S. Congress on May 30, 1854.
It allowed people in the territories of Kansas and Nebraska to decide
for themselves whether or not to allow slavery within their borders. The
Act served to repeal the Missouri Compromise of 1820 which prohibited
slavery north of latitude 36°30´.
The Kansas-Nebraska Act infuriated many in the North who considered the
Missouri Compromise to be a long-standing binding agreement. In the
pro-slavery South it was strongly supported.
After the Kansas-Nebraska Act was passed, pro-slavery and anti-slavery
supporters rushed in to settle Kansas to affect the outcome of the first
election held there after the law went into effect. Pro-slavery settlers
carried the election but were charged with fraud by anti-slavery
settlers, and the results were not accepted by them.
The anti-slavery settlers held another election, however pro-slavery
settlers refused to vote. This resulted in the establishment of two
opposing legislatures within the Kansas territory.
Violence soon erupted, with the anti-slavery forces led by John Brown.
The territory earned the nickname "bleeding Kansas" as the death toll
rose.
President Franklin Pierce, in support of the pro-slavery settlers, sent
in Federal troops to stop the violence and disperse the anti-slavery
legislature. Another election was called. Once again pro-slavery
supporters won and once again they were charged with election fraud.
As a result, Congress did not recognize the constitution adopted by the
pro-slavery settlers and Kansas was not allowed to become a state.
Eventually, however, anti-slavery settlers outnumbered pro-slavery
settlers and a new constitution was drawn up. On January 29, 1861, just
before the start of the Civil War, Kansas was admitted to the Union as a
free state.