Andrew Carnegie was a Scottish immigrant who made a fortune in the American steel industry in the late 1800s. He believed the wealthy had an obligation to donate to charitable causes. Large corporations like Rockefeller's Standard Oil grew to dominate industries by buying out competitors and creating monopolies. Mass immigration from Europe and beyond provided new workers for American factories during this period of rapid industrialization and economic growth. Immigrants struggled to adjust to life in the U.S. but gradually adopted American customs through acculturation while maintaining aspects of their original cultures. However, some nativists opposed immigration, arguing the new arrivals threatened American jobs and cultural identity.