Final answer:
Chinese immigrants comprised a significant portion of the workforce on the Central Pacific Railroad, enduring challenging conditions while contributing to a crucial infrastructure project in the American West of the 19th century.
Step-by-step explanation:
The immigrant group that made up a large part of the Central Pacific workforce was Chinese immigrants. During the construction of the Transcontinental Railroad in the 19th century, the Central Pacific Railroad hired thousands of Chinese laborers. These laborers were instrumental in laying rails across the rugged terrain of the Sierra Nevada mountains, often working under grueling and underpaid conditions. While there were other groups, including Irish and African American workers, it was the Chinese laborers who were most numerous on the Central Pacific.
The determination of the Chinese workers and their significant contribution to the railroads is a testament to their endurance amid intense hardship. It also reflects the dynamic of immigration in the American West during that period, where the influx of various groups influenced the development of the region materially and culturally. The Chinese immigrants faced severe discrimination and were targets of legislative exclusion, culminating in laws such as the Chinese Exclusion Act of 1882, which halted Chinese immigration and prevented Chinese nationals from becoming US citizens.