What was one significant contribution of immigrants to American society during the 19th century?

One significant contribution of immigrants to American society during the 19th century was the development of infrastructure, such as railroads and factories. Immigrants provided a substantial labor force that was essential for building and expanding the country’s industrial base. The influx of immigrants from various regions brought not only a willingness to work in harsh conditions but also the diverse skills needed for construction, manufacturing, and other labor-intensive sectors.

Railroads, in particular, relied heavily on immigrant labor, with many workers being employed as track layers, laborers, and in other crucial roles. These developments were pivotal in connecting different parts of the country, facilitating trade, and supporting a rapidly growing economy during the Industrial Revolution. This expansion of infrastructure was fundamental in shaping the modern United States and integrating it into a national and global economy.

Other options, while relevant to broader societal changes, do not encapsulate the direct and impactful role that immigrants had on the specific advancements in infrastructure during this period, which are foundational for America's economic growth.