Why was Andrew carnegie considered the steel king?

Andrew Carnegie was considered the "steel king" due to his pivotal role in transforming the American steel industry during the late 19th century. He founded Carnegie Steel Company, which became the largest and most profitable steel company in the world, thanks to his innovative production techniques and efficient management practices. Carnegie's emphasis on vertical integration allowed him to control every aspect of the steel manufacturing process, significantly reducing costs and increasing output. His success not only made him one of the wealthiest individuals of his time but also helped propel the United States into a leading industrial power.