Sure, the 13th amendment made it illegal, but I've certainly heard many stories of slavery continuing into the 20th century, with some guesses at even the 20's or 30's being the true end of the practice.
I understand that many slaves went back to "work" for the plantations from which they were freed, or a similar place afterwards, because they needed to do find a source of income.
After the Union armies left, what was really stopping former slave owners from re-instituting the practice in rural areas?
Is there evidence to suggest that the real end of Black slavery in this country is much later than 1865 ?
The 13th Amendment only made it illegal if you hadn't been convicted of a crime. That's where the continued practice comes in. If you write enough ridiculous laws (Black Codes) and selectively enforce them enough, you can arrest an awful lot of freedmen to force them back into slavery. This is the Convict Lease system. I couldn't say when the last example of it on a plantation was (of course, prison labor is still used by manufacturers in the US today), but World War II is usually cited as the event that made it no longer viable.