What city is the largest steel industry site in the United States? Please answer

①, Chicago is located in the heart of the North American continent, the Great Lakes iron ore region on the edge of the 1848, communicating Lake Michigan and the Mississippi River, Illinois - Michigan Canal was completed, communicating the Great Lakes and the Mississippi River between the two major waterways of navigation. In the same year, the construction of Chicago's first railroad began. Since then, Chicago began to become an important transportation hub connecting the east and west of the United States, becoming the largest railroad hub in the United States. Convenient surface transportation greatly stimulated the development of industry and commerce. Chicago became one of the most important economic centers in the United States, in the iron and steel industry, machinery manufacturing, agricultural technology, trade, culture and education are leading areas. Industry to steel, metal, food processing, electronics, petroleum processing, printing and transportation machinery and equipment industry. Iron and steel industry accounted for the first place in the United States, 1950-1960s, iron and steel production was once close to more than 100 million tons, accounting for 50% of U.S. production. There are the famous U.S. Steel (Pittsburgh relocated) and Calais Steel. Motorola, Amoco and Inland Steel are also headquartered in Chicago. Chicago is also the largest business center area and one of the largest futures markets in the U.S. Its metropolitan area has consistently ranked first in the U.S. in terms of the number of new businesses, and has been rated as the most balanced economy in the U.S. in terms of development. In addition, Chicago is home to many world-famous skyscrapers and is known as the "Home of the Skyscraper". As of July 2017, the population of the Chicago metropolitan area is approximately 2,716,000, and the population of the greater Chicago city (including suburbs) is 10 million. It is the third largest city in terms of population after New York and Los Angeles.

②, Pittsburgh (Pittsburgh) is located in the southwestern part of the U.S. state of Pennsylvania, at the mouth of the Ohio River at the confluence of the Origna River and the Montgomery Herrera River, through the Cleveland, Youngstown and the Great Lakes iron ore mining region with the canal connection, Pittsburgh is the county seat of the county of Allegheny County, but also the second largest city in Pennsylvania, after Philadelphia, in the Appalachian coalfield, one of the world's largest coal mines. Pittsburgh is the capital of Allegheny County and the second largest city in Pennsylvania after Philadelphia. Pittsburgh was once a famous steel industry city in the United States, once known as the "steel capital of the world", 1820-1940, steel production once up to 20 million tons, accounting for 40% of U.S. steel production, the world's steel production of 20%. Morgan consortium control of U.S. Steel (Carnegie Steel and United Steel and other dozens of steel companies) was set up in Pittsburgh, the headquarters. But after the 1980s, with the rise of steel production in Japan and China, the cost of the canal than the sea, Pittsburgh's steel business has been faded, relocated to the Great Lakes iron ore region on the edge of the transportation center of the city of Chicago, has been transformed into a medical, financial and high-tech industry based on the metropolis. The city's largest business is the University of Pittsburgh Medical Center, and it is also home to Pittsburgh National Bank, the nation's sixth-largest bank.

3. Youngstown is a heavy industrial city in northeastern Ohio with a population of 108,000 (1984) and a metropolitan area population of 531,000 (1980). Youngstown is located in the middle of the Ohio River - Erie Lakes Canal, 70 kilometers from Pittsburgh, in 1802 the use of nearby iron ore and charcoal development of the ironmaking industry, and then due to the development of the Allegheny Coal Fields, the opening of the Benefit Canal, Great Lakes Iron Ore District transportation of iron ore, coal mines are extremely convenient, the use of coke and Misabe iron ore development of large-scale iron and steel industry in Youngstown, in 1820 - 1900, the iron and steel production was once as high as 10 million tons, occupying 20% of U.S. steel production, and is now one of the four largest steel cities in the United States. Famous steel companies are 'and **** and the National Steel Company', United Steel Company.

④, Bethlehem is located in Pennsylvania, the United States, with a population of 100,000, near Philadelphia, New York, two major cities. One of the four major steel cities in the United States, the second largest steel company in the United States 'Bethlehem Steel Corporation' is located in Bethlehem, Bethlehem steel is the United States of America's famous marine steel, marine steel once occupied 70% of the U.S. shipbuilding industry. 1820-1900 Bethlehem's annual production of ten million tons of iron and steel, once accounted for the United States of America's iron and steel production of 20%. Bethlehem Steel declared bankruptcy in 2001.