Samuel Northup is the main character of the Novel "12 Years a Slave", which tells the story of this man from the state of New York, thas was kidnapped into slavery.
The account he left describes how terrible slavery was in central Louisiana.
"Canibals All! Or Slaves Without Masters", was written by George Fitzhugh(1806-1881). In that text, published in Richmond, Virginia en 1857, Fitzhugh refers to slavery.
He stated that you could compare workers as slaves by the way they were treated by owners in the Notrth and in the South. He wrote that labor among industrial workers in the factories of the north and England, and the slavery practiced in the southern states, both exploited workers.
But the difference in his point of view -a controversial one- was that slaves in the South were "properties" of their masters, they were treated much better than the workers from the North, who just hired and exploited them.