Why were people angry about the Kansas-Nebraska Act?

The Kansas-Nebraska Act allowed settlers in those territories to decide whether to permit slavery through popular sovereignty. This effectively repealed the Missouri Compromise restriction that had banned slavery north of the 36°30′ line, opening territory where slavery had been prohibited to the possibility of slavery. That change angered many people who opposed slavery’s expansion, so the correct choice is “It stated slavery could be legal where it had been outlawed.”

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