Answer: large numbers of surplus slaves were sold from the upper South to the lower South.
Step-by-step explanation:
As tobacco prices weakened, tobacco farmers in Virginia and Maryland developed a surplus of enslaved workers, and many of them chose to sell those slaves in the domestic slave trade that sent them to work in the Deep South.
In her novel Uncle Tom’s Cabin (1852), Harriet Beecher Stowe explains that the phrase “to be sold down the river” meant the forced migration slaves were forced to from the upper southern states to the Deep South, south from the Mississippi, to plant cotton.