What was the significance of the Kansas-Nebraska Act?

The Kansas-Nebraska Act is significant primarily because it established the principle of popular sovereignty in the newly organized territories of Kansas and Nebraska. This means that the settlers in those territories had the right to decide for themselves whether to allow slavery or not, thereby directly influencing the expansion of slavery in the United States. This act effectively repealed the Missouri Compromise of 1820, which had prohibited slavery in certain areas, leading to increased tensions between pro-slavery and anti-slavery factions. As a result, it not only heightened conflict in the territories but also contributed to a national debate over slavery that was a precursor to the Civil War. The principle of popular sovereignty would lead to violent confrontations known as "Bleeding Kansas," as both sides rushed to settle the area to influence the outcome of the slavery issue.

The act's impact extends beyond just the territories it directly addressed, as it heightened sectional divisions and transformed political alignments in the United States, thus playing a crucial role in shaping the events leading up to the Civil War.