The October issue of Reader’s Digest has an article on a lady whose job is busting slave holders in America and bringing the slaves to freedom. Pretty cool. As of Sept 22 it is not available online. When looking I found an article from 2008 about a a girl Shyima Hall, whose parents willingly sold her as a slave to a family in America for $30 a month.
Only about 2% of slaves are freed each year in the US and it usually comes from an observant person seeing something that they think is not quite right an alerting authorities which was the case for Shyima.
You can read the full article here. http://www.rd.com/your-america-inspiring-people-and-stories/slave-in-the-garage/article55737.html
Be sure to keep your eyes open as you go through life. Who knows, God might use your awareness of the issue and willingness to be get involved as a means for bringing freedom to someone held in slavery some day.