This event led to secession of seven southern states.

The correct answer is the Civil War.

Explanation:

https://en.wikipedia.org/wiki/Timeline_of_events_leading_to_the_American_Civil_War

Election of 1860

Explanation:

It was the election of Abraham Lincoln as president which caused the Southern states to secede. Lincoln was elected president on November on November 6, 1860, and secession began just a few weeks later: South Carolina went first, on December 20, followed by Mississippi on January 9, 1861, and then by Florida on the next day.For the Southern states, secession from the Union was about saving slavery.

becasue in the south they disallowed slavery but in the north slavery was illegial this boilled into because mexico wanted slavery

hope this

ghana achieved independence peacefully, while algeria gained independence through an armed struggle.