I remember as a youngster being horrified that, not so long ago, there was slavery still legal in, I think, was it Mauritania? I think so
Yes, that was one of the last to officially end it (in 1981, but no laws were passed to stop it until 2007 !).
The link I posted at the end lists countries where millions of people are living in modern-day slavery still today.
They may not always be as badly treated as slaves were in the past (sadly though, that's probably not 100% true) but they are not free to live their own lives.
There are those who claim the US prison system is a form of slavery where prisons are run for profit, with large corporations sending manufacturing work there. The same corporations that lobby for policies and prison-building investment.