Final answer:
Isabel and Ruth are sold to the Locktons in a tavern, possibly in New Orleans.
Step-by-step explanation:
Isabel and Ruth are sold to the Locktons in a tavern, according to the information given. The exact location of the tavern is not specified.
The mention of New Orleans suggests that the event took place there, as Isabel and her fellow slave were sold in New Orleans.
This information is derived from Northup's description of being sold in New Orleans, along with Eliza and her children.