How did US steel become a monopoly?

U.S. Steel became a monopoly through a series of strategic Mergers and Acquisitions, most notably the 1901 merger of Andrew Carnegie's Carnegie Steel Company with several other steel companies, creating the first billion-dollar corporation in the world. By consolidating production and resources, U.S. Steel achieved significant economies of scale, allowing it to dominate the steel market. Additionally, the company benefited from favorable rail agreements and access to vast iron ore reserves, further solidifying its monopolistic position in the industry. Regulatory environments at the time also permitted such consolidations, enabling U.S. Steel to maintain its market power.