Why did the United States want new acquisitions in the West?

United States' territory is any extent of region under the sovereign jurisdiction of the federal government of the United States,[1] including all waters (around islands or continental tracts) and all U.S. naval vessels.[2] The United States asserts sovereign rights for exploring, exploiting, conserving, and managing its territory.[3] This extent of territory is all the area belonging to, and under the dominion of, the United States federal government (which includes tracts lying at a distance from the country) for administrative and other purposes.[1] The United States' total territory includes a subset of political divisions.

Explanation:

yes he did writing dots to make the answer