Ow did the development of the modern railroad affect every day life in North America?

This is a paper for a History of Architecture class. It could deal with any aspect of the physical landscape that was modern in its time. This is why I chose the development of the modern railroad that came along with the development of the steam engine. The professor says The goal of the paper is not a descriptive essay, but an analytical study,which is why I chose the subject to be how it affected everyday life in North America. I would like it to have a large chunk be about the effect of the railroad on the expansion of the US into the west.

Please do not use sources such as Wikipedia for main ideas or large amounts of information.

Thank you!!!!!