What kind of immigrants worked for John D Rockefeller?

John D. Rockefeller employed a diverse workforce, including many immigrants, particularly in the early days of the Standard Oil Company. Many of these workers were from Europe, including Germans, Italians, and Irish, who sought job opportunities in the burgeoning oil industry. They often took on labor-intensive roles in refining and transportation, contributing significantly to the industry's growth. Rockefeller's reliance on immigrant labor reflected the broader trends of the time, as immigrants played a crucial role in the industrial expansion of the United States.