"Here is a tall bold slugger set vivid against the soft little cities," Carl Sandburg wrote of Chicago. And to this day, Chicago stands tall among American cities, especially in the importance of its modern architecture. Rebuilding from the devastating Great Chicago Fire of 1871, Chicago was the birthplace for the steel-frame skyscraper, and now claims the continent's tallest--the 110-story, 1,454-ft. Sears Tower. The Chicago River was largely responsible for Chicago's early settlement, following the discovery by French explorers Louis Joliet and Pere Jacques Marquette in 1673 that the river's arms reached nearly to the drainage basin of the Mississippi River system, forming a natural route for early trappers and traders. Chicago Union Station, completed in 1909, is the only surviving example of Chicago's great turn-of-the-century train stations. As the nation's railroad hub, Chicago once had six major rail stations: Central, Dearborn, Grand Central, LaSalle, North Western and Union.