A) Briefly explain why ONE of the following options most clearly marks the beginning of the sectional crisis that led to the outbreak of the Civil War. Northwest Ordinance (1787)

Missouri Compromise (1820)

Acquisition of Mexican territory (1848)

B) Provide an example of an event or development to support your explanation.

C) Briefly explain why one of the other options is not useful to mark the beginning of the sectional crisis.