Senator Stephen Douglas of Illinois, hoping to lure transcontinental railroad developers away from lands acquired via the Gadsden Purchase, proposed instead to build the line farther north, so that the railway would end in Chicago and give his home region a huge economic boost. But federal law required that the vast unorganized areas in the middle of the country first be carved into official territories before any track could be laid.
To do so, Douglas rammed the Kansas-Nebraska Act through Congress in 1854 to create two new territories—Kansas in the South and Nebraska in the North. According to the Missouri Compromise of 1820, both territories would have to be free because they were north of the 36˚ 30' line. But Douglas, aware that Southern legislatures would never approve two new free territories, declared instead that popular sovereignty would determine whether Kansas and Nebraska would be free or slave. In doing so, he hoped to strengthen his bid for the presidency in 1856 by winning support from Southern Democrats.
Because popular sovereignty had worked in the Compromise of 1850, Douglas assumed that the doctrine would work in the unorganized territories as well. Privately, he believed that slavery would never take hold in Kansas and Nebraska because the terrain was unsuitable for producing cotton. Popular sovereignty, then, was merely a carrot to appease the South. Douglas thus figured the act would please both the abolitionists in the North and slave owners in the South, bring development to Chicago, and increase his chances for the party’s nomination in 1856 without really changing anything.
But Douglas’s plan backfired. Southerners—Democrats and Whigs alike—jumped at the opportunity to open Northern territories to slavery, but Northerners recoiled, outraged that the Missouri Compromise had been violated. Riots and protests against the Kansas-Nebraska Act erupted in Northern cities.
What Douglas had failed to realize was that most Northerners regarded the Missouri Compromise to be almost sacred. The publication of Uncle Tom’s Cabin and the brutal enforcement of the Fugitive Slave Act had by this time awakened hundreds of thousands in the North to the horrors of slavery. Even those who benefited from Southern slavery, such as textile manufacturers, did not wish to see slavery expand further west or north. The Kansas-Nebraska Act succeeded only in shifting Northern public opinion even further away from reconciliation with the South.
The Kansas-Nebraska Act also caused the collapse of both the Whig and Democratic parties. The parties split according to section: to pass the act through Congress, Southern Whigs voted with Southern Democrats against their Northern counterparts for the first time in history. The Whigs were never able to reunite after this catastrophic divide. The Democrats survived, but Northern Democrats lost over half their seats in Congress that year.