By 1900 the US was the largest producer and also the lowest cost producer, and demand for steel seemed inexhaustible. Output had tripled since 1890, but customers, not producers, mostly benefitted. Productivity-enhancing technology encouraged faster and faster rates of investment in new plants. However, during recessions, demand fell sharply taking down output, prices, and profits. Charles M. Schwab of Carnegie Steel proposed a solution: consolidation. Financier J. P. Morgan arranged the buyout of Carnegie and most other major firms, and put Elbert Gary in charge.  The massive Gary Works steel mill on Lake Michigan was for many years the largest steel producing facility in the world.
US Steel combined finishing firms (American Tin Plate (controlled by William Henry "Judge" Moore), American Steel and Wire, and National Tube) with two major integrated companies, Carnegie Steel and Federal Steel. It was capitalized at $1.466 billion, and included 213 manufacturing mills, one thousand miles of railroad, and 41 mines. In 1901, it accounted for 66% of Americas steel output, and almost 30% of the worlds. During World War I, its annual production exceeded the combined output of all German and Austrian firms.
The  Steel Strike of 1919 disrupted the entire industry for months, but the union lost and its membership sharply declined.  Rapid growth of cities made the 1920s boom years.  President Harding and social reformers forced it to end the 12-hour day in 1923.
Earnings were recorded at $2.650 billion for 2016.