Memory Game Causes for the Civil WarOnline version Identify the causes that led to the American Civil War. by Andrew Balzer California entered as a free state Compromise of 1850 It required that all escaped slaves, upon capture, be returned to their masters and that officials and citizens of free states had to cooperate. Popular Sovereignty Sectionalism Kansas-Nebraska Act Uncle Tom's Cabin Fugitive Slave Law loyalty to one's own region or section of the country, rather than to the country as a whole It allowed people in the territories of Kansas and Nebraska to decide for themselves whether or not to allow slavery within their borders. Let the people of the territories themselves decide whether slavery would be permitted. Novel written by Harriet Beecher Stowe that showed the horrors of slavery.