Dred Scott v. Sandford
Dred Scott v. Sandford is a major American event and an integral part of The American Civil War. It is one of the two events, that needs to fire before the event starting the civil war, A House Divided (event), can fire. The other is John Brown's Last Raid. The requirements and effects of the two events are very similar, but one is for non-slave states and one is for slave states.
It has a mean time to happen of 200 months before 1845, of 100 months before 1855 and 50 months before 1860. After 1860 it has a mean time to happen of only 10 months.