What legislation called for the creation of two new territories and allowed citizens to decide on the legality of slavery there?

The Kansas-Nebraska Act of 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 for themselves whether they would permit slavery. This decision-making process presented an important shift from previous legislative compromises regarding slavery, as it essentially put the issue directly in the hands of the inhabitants of these territories rather than having Congress decide.

The act was intended to promote westward expansion and help organize the territories, but it also led to severe national tensions over the issue of slavery, directly contributing to conflict in the region known as "Bleeding Kansas." This conflict arose as pro-slavery and anti-slavery factions rushed into Kansas to influence the vote, leading to violence and turmoil. The Kansas-Nebraska Act is thus a critical turning point in American history, as it incited fierce debates and confrontations over the expansion of slavery into new U.S. territories.