What controversial bill did Stephan Douglass introduce in 1854?

In 1854, Stephen Douglas introduced the Kansas-Nebraska Act, which aimed to organize the territories of Kansas and Nebraska and allow settlers to determine whether they would allow slavery through popular sovereignty. This legislation effectively repealed the Missouri Compromise of 1820, which had prohibited slavery in those territories, leading to significant controversy and conflict, including violent clashes known as "Bleeding Kansas." The act intensified national divisions over slavery and contributed to the emergence of the Republican Party.