What principle allowed territories to decide for themselves whether to enter the Union as slave or free states?

The principle that allowed territories to decide for themselves whether to enter the Union as slave or free states is known as popular sovereignty. This approach emerged in the mid-19th century as a solution to the contentious debate over the expansion of slavery into new territories. It was championed by politicians like Senator Stephen A. Douglas, who argued that the residents of each territory should have the right to determine the status of slavery through their own voting processes.

Popular sovereignty was significant because it aimed to reduce the tension between pro-slavery and anti-slavery factions by allowing local decisions rather than imposing federal mandates. This principle played a crucial role in the debates surrounding the Kansas-Nebraska Act of 1854, where the status of slavery in those territories was left to the residents to decide, leading to significant conflict and violence known as "Bleeding Kansas."

In contrast, the Wilmot Proviso was an unsuccessful proposal to ban slavery in territories acquired from Mexico, while the Free-Soil Doctrine opposed the extension of slavery into the territories but did not endorse popular decision-making on the matter. Nativism pertains to a political policy favoring the interests of native inhabitants over those of immigrants and is not related to the question regarding statehood and slavery. Thus, popular