What was Stephan A. Douglas attempting to achieve with the Kansas-Nebraska Act?

Stephen A. Douglas was short in stature and a giant in the political arena, dubbing him the “Little Giant.” He is mostly remembered for the Lincoln-Douglas debates, (which many people believe was a debate centered around the presidential election, but was actually for the Illinois General Assembly), but he was also the author and advocate of a significant bill known as the Kansas Nebraska act.
Douglas, a proponent of Jacksonian politics, was the chair for on the Committee on Territories and was a staunch believer in the philosophy of “Manifest Destiny.” a belief that it was the U.S. destiny to expand westward all the way to the Pacific ocean.
“You cannot fix the bounds to the onward march of this great and growing country,” was a quote from Douglas on Manifest Destiny.
It was his interest in the Midwestern Transcontinental Railroad and westward settlement that spurred the Kansas Nebraska act. The railroad would be beneficial to his home state of Illinois, as well as a determining factor in westward expansion. It would open up to settlers a vast area of open land for farms and settlements
The act divided the whole Lousiana Purchase into two territories, the southern one as the Kansas territory and the northern one as the Nebraska territory, but expressed that each territory would have sovereignty. Douglas knew that he couldn’t upset the balance between pro-slave and anti-slave and therefore could choose whether each could have the issue of slavery determined. This upset the North because it basically rendered the Missouri Compromise useless and the south loved it because it gave more territory for pro-slave expansion.
Many believe that this was the number one cause of the Civil War.

Two pressing issues occupying American politics prior to the Civil War converge in the Kansas-Nebraska Act: slavery and westward expansion.
Settlers seeking to stake a claim in what would become Nebraska were prevented from doing so because it was not a territory. The Missouri Compromise prevented slavery north of the line running along the southern border of Missouri. Southerners did not want a new state north of the line to upset the balance of powers regarding slave states. Douglas proposed the Kansas-Nebraska Act, which allowed people in these two territories to decide for themselves if they wanted to allow slavery. This undermined the longer-standing Missouri Compromise, and likely proved one of the more decisive events leading to the Civil War.
The abolitionist John Brown became involved in the violence that ensued as a result of this act, in what is known as Bleeding Kansas. While Nebraska was securely an anti-slavery state, Douglas assumed Kansas would be pro-slavery, keeping the number of Northern and Southern states the same as before the act. However, he underestimated the resistance to slavery some in Kansas would have and the level of violence that would result.
This acrimony eventually led not only to the Civil War but also to the destruction of the Whig Party. After this act, Northern and Southern Whigs split form each other, with Southern Whigs joining the Democratic Party and the Northern Whigs forming the Republican Party, soon to be associated with Abraham Lincoln.