Tianjin and Chicago are friendly associated on April, 21st , in 2008.

Chicago is the largest city in the U.S. state of Illinois.With a population of 2,853,114(2008), it ranks the 3rd largest city in the United States.

Chicago has been rated as having the most balanced economy in the United States,due to its high level of diversification. The city was named the fourth most important business center in the world in the MasterCard Worldwide Centers of Commerce Index. In 2008, Chicago placed 16th on the UBS list of the world's richest cities. It is a major world financial center, with the second largest central business district in the U.S.It is also the headquarters of the Federal Reserve Bank of Chicago, home to three major financial and futures exchanges, including the Chicago Stock Exchange, the Chicago Board Options Exchange (CBOE), and the Chicago Mercantile Exchange (the "Merc"), which includes the former Chicago Board of Trade (CBOT). Perhaps due to the influence of the Chicago school of economics, the city also has markets trading unusual contracts such as emissions (on the Chicago Climate Exchange) and equity style indices (on the U.S. Futures Exchange).

Manufacturing, printing, publishing and food processing also play major roles in the city's economy. Several medical products and services companies are headquartered in the Chicago area, including Baxter International, Abbott Laboratories, and the Healthcare Financial Services division of General Electric.

Chicago is a major transportation hub in the United States. It is an important component in global distribution, as it is the third largest inter-modal port in the world after Hong Kong and Singapore.Additionally, it is the only city in North America in which six Class I railroads meet, about one-third of the country's freight trains pass through the city, making it a major national bottleneck. Besides, Chicago is served by Midway International Airport on the south side and O'Hare International Airport, the world's second busiest airport, on the far northwest side. In 2005, O'Hare was the world's busiest airport by aircraft movements and the second busiest by total passenger traffic (due to government enforced flight caps).

Chicago has been a world center of higher education and research with several universities that are in the city proper or in the immediate environs. These institutions consistently rank among the top "National Universities" in the United States, include the University of Chicago, which also ranks among the world's top ten; Northwestern University, the University of Illinois at Chicago,etc.

Globally recognized,  Chicago has numerous nicknames, of which the best known is "Windy City".  Due to the city generally being the second most prestigious in the nation in terms of culture, entertainment, and finance, Chicago has a heritage for hosting major international, national, regional, and local events that include commerce, culture, entertainment, politics, and sports.