Final answer:
Option 1. The railroad was the technological phenomenon that facilitated economic and political expansion in the early nineteenth century, supporting the growth of American cities, industrial expansion, and European imperialism.
Step-by-step explanation:
The technological phenomenon that facilitated economic and political expansion in the early nineteenth century is the railroad. The railroad, along with the telegraph, steamboat, and the Maxim gun, played a pivotal role in advancing expansionism and imperialism during this era. The transcontinental railroad particularly spurred industrial expansion post-Civil War, transforming the United States economically and socially as it catalyzed a shift from rural to urban centers, increased the population due to immigration, and accelerated the development and spread of innovations such as steel manufacturing, the telephone, and the light bulb.
Technology enabled not just American expansionism but also European imperialism, as it allowed a small number of Europeans to dominate vast territories. The railroad was crucial in the United States for shipping resources, aiding in federal centralization, and helping establish a national market system. It was also instrumental during the Civil War, improving transportation of troops and war materiel. In the broader context of the Second Industrial Revolution, the demand for raw materials fueled imperialism, providing resources necessary for the technological advancements of the era.