http://www.naplesnews.com/news/2010/mar/03/farmworker-slaver... and http://www.tampabay.com/opinion/columns/modern-day-slavery-m... are some articles about recent situations in Florida.
There's also domestic servant slavery and even factory worker slavery, such as the slaves that are imported to US Territory Saipan to work in Chinese owned garment factories. (http://articles.sfgate.com/1999-01-22/news/17677080_1_garmen...) Workers there are raped by managers, kept in guarded chained enclosures, and have to undergo forced abortions when they get pregnant from the rapes.
There's also legal slavery, such as prison labor, which is explicitly permitted under the Constitution, although many legal experts believe that it actually has to be part of the sentence as punishment for the crime, and not just something that applies to all prisoners without a judge's approval during sentencing. To simplify things we'll skip those as being "OK" slavery since some believe there is legal justification for it even when not part of sentencing. Don't want to confuse the issue.
By slavery we mean you are not free to leave and you are not paid wages for your work. Many workers in the US are even shackled up and beaten.
Gosh look I even just now found a new book on Modern American Slavery.
Of course there was also slavery of black people in the US that lasted until the 1940s. Oh, didn't know about that? http://www.slaverybyanothername.com/
Most people prefer not to know why the goods and food they buy are so cheap.
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