1856 Five proslavery settlers in Kansas are killed by John Brown and his men in the Pottawatomie Creek Massacre. The Republican Party platform calls for admitting Kansas as a free state. The merchant ship Erie is seized by federal forces with a cargo of 890 slaves. Her captain, Nathaniel Gordon, is hanged in 1862. The Civil War begins.
Slavery is banned in the Nebraska Territory.
Congress forbids slavery in all non-state territories and in the District of Columbia. Owners are promised compensation. Second Confiscation Act emancipates all slaves whose owners are in rebellion against the United States. Maryland's state constitution is amended to abolish slavery.