What effect did the NPRRs monopoly have on the nature and environment of the Park?

The research paper is for my History of Yellowstone Class with the topic of the Northern Pacific Railway’s relation to Yellowstone National Park. Here is a thesis I came up with earlier this semester (feel free to come up with your own) and my professor’s comments on it:
Thesis-The Northern Pacific Railroad Company supported the creation of Yellowstone National Park as a means to expand its franchise and gain economic opportunities.
Professor’s Comments-
This a good argument, but is it a new argument? How will your thesis build upon the work of previous historians?
It may be useful to consider this thesis within the wider treatment of the history of the railroads. Two interesting books that came out recently are Railroaded and Sunset Limited which look at the role of railroads in the United States. They note interesting things about the railroads that could be compared to what happened in Yellowstone.
It is also worth considering where the NPRR was successful in their exploitation and where they were defeated in their efforts.
Also, what effect did the NPRRs monopoly have on the nature and environment of the Park?
Do you think we would have Yellowstone without the NPRR?

The beginning of the paper should discuss a brief history of railroads’ (Northern Pacific, Great Northern, Milwaukee, etc.) crucial role in developing the American west, specifically Montana.
(a brief, general history of Northern Pacific Railway and Yellowstone National Park needs to be included) Discuss how railroads’ increasing involvement in Yellowstone National Park was a result of railroads role in Montana’s development with a history of Northern Pacific Railway’s relation to Yellowstone National Park: how it influenced the development of the park, its early interests with the early expeditions of Yellowstone, promotion of the park and tourism, how NPRR influenced the way the park was enjoyed, involvement in the creation of towns related to Yellowstone, construction of hotels and other commodities to ensure tourists comfort, dude ranches, NPRR relations with other businesses, agencies, and key characters and other transportation systems in Yellowstone National Park, why a rail-line through the park wasn’t permitted-opposition. (Not all of these topics need to be included, just examples of what needs to be in the paper). The paper should wind down with the eventual loss of railroads’ importance to Yellowstone National park. End with a summary of paper and conclude with why the Northern Pacific Railroad was so important to the Park’s development-what would the park look like without it. Primary resources are required for the paper; newspaper articles, posters, Northern Pacific Railway pamphlets, guidebooks, and magazines are great resources. Images may be used but are not included in the length of the paper (must be 10 pages WRITTEN) if Images are used they should be included at the end of the paper with references of Figure 1, 2, etc. in text. Secondary sources are also required.
Here is a list of suggested sources:
Mickelson, Sig. The Northern Pacific Railroad and the Selling of the West : A Nineteenth-Century Public Relations Venture. Prairie Plains Series. Sioux Falls, SD: Center for Western Studies, 1993.