Why do you think there was slavery in the south, but not in the north?

The south relied on agriculture as the north wasn't heavily focused on agriculture

The Southern part of the United States relied heavily on agriculture. This required manual labor. For them it was a lot cheaper to use slaves to keep their economy strong.

However, the North wasn't as focused on agriculture. Instead, they relied on industrialsm. Industrial jobs like factory workers, required a necessary ammount of knowledge. Slaves were deprived of this necessary knowledge, therefore they were not capable of performing these jobs.