Final answer:
The people moved into the old northwest for various reasons, including the opening of the area to settlement, the weakening of the Indian threat, the acquisition of cheap and productive land, and the expansion of the territory where slavery was legal. However, they did not move to escape the domination of wealthy plantation owners. Therefore, the correct option is D.
Step-by-step explanation:
The people moved into the old northwest for all of the following reasons except to escape the domination of wealthy plantation owners. They moved for various reasons such as the canal and highway boom that opened the area to settlement, the weakening of the Indian threat, the acquisition of cheap and productive land, and the expansion of the territory where slavery was legal. These factors led to greater mobility among the American people, the spread of settlements beyond the Appalachian Mountains, and the provision of raw materials for factories in the Northeast.