What technological innovation did Andrew Carnegie bring to the steel industry and how did it affect economic development in the U. S.?

Andrew Carnegie is the the leader of the American steel industry from 1873 to 1901. He is famous for his technological innovations. H e began the vertical integration, meaning it owned all of then different businesses on which it depends for its operation. He bought coal mines, limestone quarries, and iron ore fields. It saved money and enabled many companies to expand.