Many events contributed to several Southern states seceding from the Union in 1860. One important event was the election of Lincoln.
The election of Abraham Lincoln of the newly-formed Republican Party, which had banned the creation of any new slave-states.
Fort Sumter started the American Civil War.
The Civil War, a devastating and tragic event in United States' history, can never be forgotten.
it was a key event in the run up to the english civil war
The secession of South Carolina from the Union
The election of Abraham Lincoln in November 1860.
the election of Abraham Lincoln.
The event that the Civil War had the federal government was the Secession of the Southern States.
the nullification crisis
Lincoln's election - followed immediately by the secession of South Carolina, and then Lincoln's rejection of the final attempted compromise, because it would have allowed some extension of slavery.
An unexpected event, such as a terrorist attack, is an immediate crisis, and does not allow for research and planning.
The Manchurian crisis
The secession of the Western Counties of Virginia from the Confederate State of Virginia.
The 1860 election of President Abraham Lincoln
I'm assuming that you are talking about the rebellion of the 11 seceding states that made up the Confederate States of America. This event is particularly important in American History because our country was essentially fighting itself. The event succeding the secession, which was the Civil War, was also the bloodiest war up until then.