The City of Chicago is the third-most populous city in the United States and the most populous city in both the state of Illinois and the Midwestern United States. In terms of wealth and economy, Chicago is considered one of the most important business centers in the world. Chicago was incorporated as a city in 1837, near a portage between the Great Lakes and the Mississippi River watershed, and grew rapidly in the mid-nineteenth century. After the Great Chicago Fire of 1871, which razed several square miles and left more than 100,000 homeless, the city made a concerted effort to rebuild on the damage. The construction boom accelerated population growth throughout the following decades, leading Chicago to become among the five largest cities in the world by 1900. During this period Chicago is noted for its contribution to urban planning and zoning standards, new constructions styles (including the Chicago School of architecture), the embracement of the City Beautiful Movement, and the eventual creation of the steel-framed skyscraper. Positioned along Lake Michigan, the city is an international hub for finance, commerce, industry, technology, telecommunications, and transportation: O'Hare International Airport is the second-busiest airport in the world when measured by aircraft traffic; the region also has the largest number of U.S. highways and rail road freight. Landmarks in the city include Millennium Park, Navy Pier, the Magnificent Mile, Art Institute of Chicago, Museum Campus, the Willis (Sears) Tower, Museum of Science and Industry, and Lincoln Park Zoo. Chicago's culture includes the visual arts, novels, film, theater, especially improvisational comedy, and music, particularly jazz, blues, soul, hip hop, gospel and house music. There are many colleges and universities in the Chicago area; among these, Northwestern University, University of Chicago, and the University of Illinois at Chicago are classified as "highest research" doctoral universities. Additionally, Chicago has professional sports teams in each of the major professional leagues. The city has many nicknames, the best-known being the Windy City.