The Colorado Fuel and Iron Company (CF&I) began production in 1872 and grew to become the largest steel mill in the Western United States and a firm of enormous importance to the industrialization of the American West. The first steel mill west of the Mississippi River, CF&I also played a pivotal role in the tumultuous history of American labor relations. By the turn of the 20th Century the company was the largest private landowner and the largest employer in Colorado. CF&I mines and mining towns operated throughout the West, while subsidiary companies stretched from Massachusetts to California. Its mills in Pueblo, Colorado provided iron and steel products for agriculture, transportation, mining and other industries critical to western development. The company fueled immigration of ethnic groups to work in its mines and mills, playing an important cultural role in diversifying a burgeoning population.