Well it depends what they are in need of. They most commonly would want more land for their country to build and farm on. They may want land with fertile soil for farming. They may want the land because of it's geography, for example, for simple trade routes leading to and from the areas around north America (Canada, Mexico) etc.
My guess would be the first one
Answer: Before permanently settling the western territories, the United States had to consider the presence of Native Americans already living on these lands. Great Britain may have agreed to give the United States the land, but no one had consulted with the Indian people concerning this change. Reacting to the pressure of American settlers anxious for new land, Congress sought treaties with Native Americans to insure the safety of the settlers, and to obtain clear title for the land.
Explanation:
<span>a belief or theory that opinions and actions should be based on reason and knowledge rather than on religious belief or emotional response.</span>