Immigrants contributed greatly to American growth in many ways. The first major wave of immigration began in 1880 and consisted mostly of free Europeans and slaved African and Caribbeans. Over the span of almost 50 years, the population grew by more than 25 million people, which was more than a quarter of America's habitants back then.
Population growth aside, the massive amount of immigrants led to big economical and social chages, as European workers got into poorly paid jobs with terrible conditions, had whole families share a small room, and augmented the need for a growth in forms of transport as well.