Senator John C. Calhoun said, "We have conquered many of the neighboring tribes of Indians, but we have never thought of holding them in subjection—never of incorporating them into our Union....To incorporate Mexico, would be the very first instance of the kind of incorporating an Indian race; for more than half of the Mexicans are Indians, and the other is composed chiefly of mixed tribes.... Ours, sir, is the Government of a white race.... [I]t is professed and talked about to erect these Mexicans into a Territorial Government, and place them on an equality with the people of the United States. I protest utterly against such a project."

The excerpt most directly reflects which of the following developments in the United States during the first half of the nineteenth century?

Options:
A The end of the Spanish-American War

B Westward expansion

C The booming internal slave trade

D: Increased manufacturing