The fight over slavery impacted the American expansion westward, as it forced both sides to try to compromise. On one hand, the South did not want more "free" lands given to the already powerful North, in which there would be even more territory for slaves to run away too, while the North did not want slavery to spread westward.
The compromise was that 3/5 of the slaves were counted as population, the North would own the states north of the Mason-Dixon line that was drawn across the west, but would be forced to catch runaway slaves and return them.
