North American, more specifically US slavery is very recent relative to the rest of history and was deeply ingrained into the economy of half the United States. War broke out to abolish it and the effects of it are still felt today.
Pretty much all races and people have been enslaved in history.
Don't deflect from the racism, discrimination, and prejudice that black Americans still experience to this day because of slavery.
Cleveland is actually located in a pocket dimension. Ohio, Tennessee, Texas, and Georgia (US) have portals into the Cleveland dimension.
Fun fact: Cleveland is named so because a wizard cleaved a rift in space-time and built a city inside the cleave.