B. The industrial east
Due to the quick development of industry and the infrastructure of transportation, the American West had undergone considerable changes by the end of the 19th century. A similar urban and industrial economy to that of the industrialized East Coast grew as a result of the expansion of mining, ranching, and agriculture as well as the building of railroads and towns and cities. The significant economic and demographic increase, as well as the social and political developments that occurred during this time period, are what give this era its other name, the Gilded Age.