From the publisher's website:-
'Go West! In the mid-1800’s this cry was the embodiment of the young nation’s belief in Manifest Destiny, that the United States should expand across the continent. While some of the early Railroad Barons felt it was best to focus on developing the economy in the Eastern U.S., new riches and lucrative opportunities awaited in the Wild West. Those who had the courage to build over the Rockies or through the Sierra Nevada and connect the East and West joined the pantheon of railroad visionaries.
Do you have the skill to tame the West and be as successful as those who came before you? Railways of the Western U.S. is an expansion map for Railways of the World. You will need the pieces from Railways of the World (track and city tiles, bonds, money, empty city markers, trains and first player marker) to play Railways of the Western U.S.'