What name was given to the vast arid territory between the Mississippi River and the Pacific Coast, which includes the Great Plains and Rocky Mountains?

The vast arid territory between the Mississippi River and the Pacific Coast, which encompasses significant features like the Great Plains and the Rocky Mountains, was often referred to as the "Great American Desert." This term was commonly used in the mid-19th century to denote the perception of this region as inhospitable and largely uninhabitable, primarily due to its dry climate and rugged terrain.

The name reflected the early American view of the West before the realities of agricultural expansion and settlement were fully understood, particularly after advancements in farming techniques and the development of irrigation. The term emphasized the aridity and challenges posed by this region, even though it would later be recognized for its agricultural potential and valuable resources.

Other options refer to specific aspects of this vast area. The Great Plains is a geographical region known for its flat terrain and prairie landscapes, encompassing parts of the territory but not representing the entire area in question. The Mining Frontier relates to the areas in the West where gold and silver mining became prominent during the Gold Rush, while the Oklahoma Territory specifically refers to a distinct region that was set aside for Native American tribes and later opened to settlers, making it a narrower focus than the entirety of the Great American Desert.