(1) Chicago is located in the center of the North American continent, on the edge of the Great Lakes iron ore district. 1848, the Illinois-Michigan Canal connecting Lake Michigan and Mississippi River was completed, which communicated the shipping between the two waterways. In the same year, the first railway in Chicago began to be built. Since then, Chicago has become an important transportation hub connecting the east and west of the United States and the largest railway hub in the United States. Convenient land and water transportation has greatly stimulated the development of industry and commerce. Chicago has become one of the most important economic centers in the United States. It is a leading region in steel industry, machinery manufacturing, agricultural technology, trade, culture and education. The industries are mainly steel, metal, food processing, electronics, petroleum processing, printing and transportation machinery and equipment. The steel industry ranks first in the United States. In the 1960s, the steel output was close to 1 100 million tons, accounting for 50% of the American output. There are famous American Steel Company (moved from Pittsburgh) and Calais Steel Plant. Motorola, Amoco and Inland Steel are also headquartered in Chicago. Chicago is also the largest commercial center and one of the largest futures markets in the United States. The number of new enterprises in its metropolitan area has always ranked first in the United States and has been rated as the most balanced economy in the United States. In addition, there are many world-famous high-rise buildings in Chicago, which is known as the "hometown of skyscrapers". As of July 20 17, the population of downtown Chicago is about 2710.6 million, and the population of greater Chicago (including suburbs) is10 million. It is the third most populous city after new york and LA.

(2) Pittsburgh is located in the southwest of Pennsylvania, USA, where the Aulina River and the Mont Mehra River meet to form the mouth of the Ohio River, which is connected with the iron ore areas of the Great Lakes through Cleveland and Youngstown. Pittsburgh is the county seat of Allegheny County and the second largest city in Pennsylvania after Philadelphia. It is located in the center of Appalachian Coalfield, which is one of the largest coal mines in the world. Pittsburgh was once a famous steel industrial city in the United States and was once known as the "steel capital of the world". 1820- 1940 steel production reached 20 million tons, accounting for 40% of the steel production in the United States and 20% of the steel production in the world. The headquarters of American steel companies controlled by Morgan Consortium (composed of Carnegie Steel Company and United Steel Company) is located in Pittsburgh. However, after the1980s, with the increase of steel production in Japan and China, the cost of the canal was lower than that of shipping. Pittsburgh's steel business has faded out and moved to Chicago, a transportation center city on the edge of the Great Lakes iron mine area, and now it has been transformed into a city with medical, financial and high-tech industries as the mainstay. The largest enterprise in the city is the University of Pittsburgh Medical Center, and it is also the location of Pittsburgh National Bank, the sixth largest bank in the United States.

③ Youngstown is a heavy industrial city in the northeast of Ohio, with a population of 108000( 1984) and a metropolitan population of 53 1000( 1980). Youngstown is located in the middle of the Ohio River-Lake Erie Canal, 70 kilometers away from Pittsburgh. 1802, the ironmaking industry was developed by using nearby iron ore and charcoal. Later, due to the development of Allegheny coalfield and the opening of the canal, the transportation of iron ore and coal mines in the Great Lakes iron mine area was extremely convenient. Youngstown developed a large-scale steel industry by using coke and Misabi iron ore 1820-65438+. Well-known steel companies include Hehe Heguo Steel Company and United Steel Company.

(4) Bethlehem is located in Pennsylvania, USA, with a population of 65,438+million, adjacent to Philadelphia and new york. Bethlehem Steel Company, one of the four largest steel cities in the United States, is located in Bethlehem, the second largest steel company in the United States. Bethlehem Steel is a famous American marine steel, which once occupied 70% of the American shipbuilding industry. 1820- 1900, Bethlehem produced10 million tons of steel every year, which once accounted for 20% of American steel production. 200 1 Bethlehem steel company declared bankruptcy.