Answer:
The election of Abraham Lincoln as President of the United States in 1960.
Step-by-step explanation:
Abraham Lincoln was elected president in 1960. He was the first president of newly created Republican Party, which ran an anti-slavery, or abolitionist platform.
Abraham Lincoln opposed the expansion of slavery in the new western U.S. territories but he did not explicitely say that slavery in the South should end, however, the Southern states saw his positions as a threat to slavery and decided to secede.