Did the system change enough to liberate the slaves?
It was most of a yes and no. The South did have slavery but in the north and other territories, there was no slavery.

1)Northwest ordinance
No slavery

2)Manifest destiny
No slavery in future territories

3)Emancipation proclamation
Freed all slaves

4)Kansas-Nebraska Act
No slavery

5) Fugitive slave act
Slaves can be reclaimed if they runaway to the north

6) Southern homestead act of 1866
Gave ownership rights to all black and whites