Which legislation promoted the organization of territories where the decision on slavery would be made by local settlers?

The Kansas-Nebraska Act of 1854 is significant because it established the principle of popular sovereignty, which allowed local settlers in those territories to decide whether to allow slavery within their borders. This act effectively repealed the Missouri Compromise, which had previously prohibited slavery in certain areas, and it created two new territories, Kansas and Nebraska. The expectation was that the residents of these territories would determine their own laws regarding slavery, shifting the focus of the debate over slavery from Congress to the local populace. This decision led to increased tensions and conflicts, particularly in Kansas, as pro-slavery and anti-slavery settlers moved into the territory to influence the outcome, contributing to a period of violent conflict known as "Bleeding Kansas."