Chicago is the largest city in both Illinois and the Midwest, and the third most populous city in the United States, with over 2.8 million living within the city limits. Chicago was founded in 1833, near a portage between the Great Lakes and the Mississippi River watershed. The city became a major transportation and telecommunications hub in North America. Today, the city retains its status as a major hub, both for industry and infrastructure, with O'Hare International Airport being the second busiest airport in the world. In modern times, the city has taken on an additional dimension as a center for business and finance and is listed as one of the world's top ten Global Financial Centers.The World Cities Study Group at Loughborough University rated Chicago as an "alpha world city" due to Chicago's important role in the global economic system.