Final answer:
Baltimore became a key city in the domestic slave trade in the US after 1808 due to the ban on importing slaves from Africa and the surplus of slaves in the Upper South. Slaves were brought from the East and West to major markets like New Orleans and Natchez to be sold.
Step-by-step explanation:
In the United States, Baltimore became a key city in the domestic slave trade after 1808 due to several factors. The ban on importing slaves from Africa led to a high demand for domestic slaves. Additionally, the shift from tobacco to wheat farming in the Upper South resulted in surplus slaves in states like Virginia and Maryland, who were then sold to meet the growing demand for labor in the South. New Orleans and Natchez became major slave markets where slaves from the East and West were brought to be sold.