Final answer:
The West was the least densely populated region in the United States in 1890, influenced by its large undeveloped areas and fewer economic activities compared to other regions.
Step-by-step explanation:
In 1890, the West was the least densely populated region of the United States. During this time, the population distribution was greatly influenced by economic activities and geographical characteristics. The Northeast was the most densely populated due to its megalopolis stretching from Washington, D.C. to Boston. The South had established agricultural economies, and the Midwest was developing with people migrating from other regions seeking new opportunities. However, the West, despite its vast size, was sparsely populated with significant areas still relatively undeveloped and difficult to inhabit, especially due to its rugged terrain and possible lack of economic incentives compared to other regions.