Which industry did Andrew Carnegie predominantly control?

Andrew Carnegie predominantly controlled the steel industry, which played a pivotal role in America's industrial growth in the late 19th century. He founded the Carnegie Steel Company, which became one of the largest and most profitable steel companies in the world. Carnegie was known for his innovative production techniques and focus on efficiency, allowing him to reduce costs and increase output substantially. His leadership in steel production not only contributed to the infrastructure development, such as railroads and buildings, but also positioned him as a key figure in the philanthropic efforts that followed his success in the industry. Carnegie's influence was so significant that he is often associated with the growth of the American steel industry and its impact on both the economy and society during that period.