Final answer:
The Kansas-Nebraska Act led to the start of the Civil War.
Step-by-step explanation:
The Kansas-Nebraska Act was a major event that led to the start of the Civil War. It was enacted in 1854 and allowed for popular sovereignty in the territories of Kansas and Nebraska, meaning that the residents of those territories could vote on whether to allow slavery. This act repealed the Missouri Compromise of 1820, which had prohibited slavery in those territories. The act intensified the tensions between the North and the South, ultimately leading to the outbreak of the Civil War in 1861.
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