If I remember my history right, here goes. Lincoln was a republican, they were anti-slavery. He campaigned against extending slavery, not abolishing it. He and everyone knew that the existence of the south as it was, there was no way they could end slavery in the area. The North depended on the south to produce for them too. What happened was the south took offense to his position and said that they would secede from the union if he won. Lincoln was not about to let this happen. When the south did it though the war began and Lincoln thought it would be an easy win. He was wrong and completely underestimated the south's will to keep their way of life. When it looked like the war would never end, Lincoln had a meeting to see if deporting all the slaves would work to end the war. Things starting getting so bad and the deaths were high on the Union's side. They had to get immigrants, that could not even speak English to fight for the Union, they were running out of men. That is when Lincoln decided to free the slaves, it was to end the war. Which it did. The south was kept under military law for years and made to suffer greatly for the treason that Lincoln believed they committed.
There were hardly any northern slaves. When the slaves were free some headed north. They were not completely welcome. The Northerners were not accustomed to them and their ways. It made things a bit uncomfortable for all. Most of the slaves returned to the south and returned to their previous owners or were given land by the federal government to live on.