The Loop is the central business district or downtown of Chicago, Illinois. It is one of the city's 77 designated community areas. The Loop is home to Chicago's commercial core, City Hall, and the seat of Cook County. In the late nineteenth century, cable car turnarounds and prominent elevated railway encircled the area, giving the Loop its name. The community area is bounded on the north and west by the Chicago River, on the east by Lake Michigan, and on the south by Roosevelt Road, although the commercial core has expanded into adjacent community areas. As a business center, some of the corporations the Loop hosts include the Chicago Mercantile Exchange (CME), the world's largest options and futures contracts open interest exchange; the headquarters of United Continental Holdings, one of the world's largest airlines; AON; Blue Cross Blue Shield; Hyatt Hotels Corporation; BorgWarner, and other major corporations. The Loop is home to 500 acre Grant Park; State Street, which hosts a historic shopping district; the Art Institute of Chicago; several theaters; and numerous subway and elevated rapid transit stations. Other institutions in the Loop include the Willis Tower, once the tallest building in the world, the Chicago Symphony Orchestra, the Lyric Opera of Chicago, the Goodman Theatre, the Joffrey Ballet, the central public Harold Washington Library, and the Chicago Cultural Center. In what is now the Loop, on the south bank of the Chicago River, near today's Michigan Avenue Bridge, the US Army erected Fort Dearborn in 1803. It was the first settlement in the area sponsored by the United States. In 1908, Chicago addresses were made uniform by naming the intersection of State Street and Madison Street in the Loop as the division point for designating addresses, North, South, East or West on the Chicago street grid. - source: Wikipedia