Because of the characteristics of steel, bridges, sports and robot manufacturing, Pittsburgh is nicknamed the city of steel, the city of bridges, the city of champions and the city of robots.

At the beginning of the 20th century, Pittsburgh's industry and commerce developed rapidly, becoming the center of the American industrial revolution, and a large number of pioneers of the industrial revolution were born. Andrew carnegie, the king of steel, established Carnegie Steel Company (later became the American Steel Company), which once monopolized more than half of the steel production in the United States and became the trust of the steel industry; Andrew Mellon founded the Mellon consortium, became the richest man in the United States at that time, and later became the US Treasury Secretary; George Westinghouse, American engineer and manufacturer. Many of its inventions have won more than 400 patents, including air braking (1869), railway braking signal facilities (1882) and practical methods of power transmission. He founded Westinghouse Electric Company at 1886. Heinz founded the world food giant Heinz Company.

From the geographical environment, the surrounding areas of Pittsburgh are rich in bituminous coal, limestone and iron ore, and the inland ports have convenient transportation, which has good conditions for large-scale development of iron and steel industry. From the perspective of historical development, by the 1980s of 19, this region had developed into the largest steel base in the United States, and its steel output value accounted for nearly two-thirds of that of the United States at that time. Before and after World War I, American heavy industry and railway construction developed rapidly. During World War II, the demand for steel soared due to the war. Pittsburgh entered the "golden age" of iron and steel industry development. The development of iron and steel industry has promoted the economic development of this area. Among the top 500 American enterprises selected by Fortune magazine at that time, 2 1 companies were headquartered in Pittsburgh, such as American Steel Company, Westinghouse Electric Company and Alcoa Company. Metallurgy, coke, heavy electrical manufacturing equipment and glass industry were the pillar industries of the regional economy at that time, which concentrated most of the local employment. However, because the regional economy relies too much on the iron and steel industry, it has caused serious environmental pollution, high industrial concentration and single employment channels.