When was slavery abolished in the northern states?

On January 1, 1863, using his authority as commander in chief, Lincoln issued the Emancipation Proclamation, declaring that the slaves in areas "in rebellion against the United States" were free as of that date. It specifically exempted border states in order to retain the support of Unionists in those areas. (Tennessee, although exempted, ended slavery of its own volition.)

The emancipation of all slaves was attained with the passage of the 13th Amendment in 1865. Lincoln's refusal to compensate slave owners for their property was embodied as constitutional policy in the 14th Amendment, ratified in 1868.

It must be noted that Slave Owners in Delaware sued Congress and were granted compensation for Slaves conscripted by the Union Army.