Which act, proposed by Stephen Douglas in 1854, allowed new states to decide their slavery status via popular sovereignty?

The Kansas-Nebraska Act, proposed by Stephen Douglas in 1854, is significant because it introduced the concept of popular sovereignty, which allowed the settlers of the new territories of Kansas and Nebraska to determine whether they would permit slavery. This act effectively repealed the Missouri Compromise of 1820, which had prohibited slavery north of the 36°30′ parallel, and was aimed at facilitating the expansion of the United States westward.

By promoting popular sovereignty, the Kansas-Nebraska Act aimed to resolve the contentious debate over whether new territories should be free or slave states in a way that rested on the will of the local settlers. This led to violent conflicts, known as "Bleeding Kansas," as pro-slavery and anti-slavery factions rushed into the territories to influence the vote. The act ultimately intensified the national debate over slavery and contributed to the polarizing tensions that led to the Civil War.

In contrast, the Fugitive Slave Act was related to the capture and return of runaway slaves, the Compromise of 1850 was an attempt to ease tensions by balancing free and slave states, and the Missouri Compromise sought to maintain the balance between free and slave states at a point before the Kansas-Nebraska Act changed the legislative