Final answer:
The Kansas-Nebraska Act allowed the residents of Kansas and Nebraska to vote on the issue of slavery, leading to violent conflicts and the formation of the Republican Party. These events ultimately contributed to the Civil War.
Step-by-step explanation:
The Kansas-Nebraska Act, passed in 1854, allowed for popular sovereignty in the territories of Kansas and Nebraska, meaning that the residents could decide if they wanted slavery or not. This act resulted in violent conflicts between pro-slavery and anti-slavery factions in Kansas, known as Bleeding Kansas. It also led to the formation of the Republican Party, which opposed the expansion of slavery and ultimately contributed to the outbreak of the Civil War.
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