Chicago is the third most populous city and the second largest hub of heavy industry in the United States. Over one thousand exhibitions and conventions are held annually, and the Chicago Mercantile Exchange is truly the world's biggest and most well-known futures exchange. Benefiting from its geographical advantages, Chicago has been a center of trade in North America with the O'Hare International Airport and Great Lakes Waterway.
Former Mayor Hur Nam-sik and Mayor Daley declared the City of Chicago and Busan Metropolitan City sister cities on May 7, 2007 during Mayor Hur's visit to Chicago.