Final answer:
The Kansas-Nebraska Act proposed by Senator Stephen A. Douglas reignited tensions between the North and South over slavery. It repealed the Missouri Compromise line and introduced popular sovereignty, causing disagreement between northerners and southerners. This act played a significant role in sparking the conflict that led to the Civil War.
Step-by-step explanation:
The Kansas-Nebraska Act proposed by Senator Stephen A. Douglas in 1854 reignited tensions between the North and South over the issue of slavery. The act repealed the Missouri Compromise line and allowed for the principle of popular sovereignty, which meant that the people of Kansas and Nebraska could decide for themselves whether to adopt slavery. This caused anger among northerners who opposed the extension of slavery into new territories, while pleasing southerners who wanted federal protection for slavery. The act further divided the nation and contributed to the growing conflict that eventually led to the Civil War.