Why is the louisiana purchase treaty an important document in the study of manifest destiny? a.) it provides an insightful history of new orleans before it joined the united states. b.) it indicates just how prosperous the united states was becoming. c.) it illustrates the relationship between the united states and france. d.) it shows the extent to which the united states was claiming land westward.

The correct answer here is the option D.

Manifest Destiny was an idea and an ideology that was dominant during the development of the United States. As they became an independent nation this idea became even more clear. Manifest Destiny describes the belief of the US settlers that it was their destiny and their duty, bestowed upon them by God to acquire all the lands in the North America. The Louisiana purchase shows how the US expanded westward with this belief in mind. 

The Louisiana Purchase treaty is an important document in the study of Manifest Destiny because it shows the extent to which the United States was claiming land westward. The correct answer is D.