Emily Graslie at the Field Museum in Chicago has a great video series where she talks about almost anything and everything. In this episode, she talks about the 1893 World's Columbian Exposition.
Chicago would later go on to host the 1933-1934 Century of Progress Exposition, but lesser known, even in Chicago, were the plans to host Expo '92 there, in conjunction with Seville's Expo '92. Sadly, Chicago's plans was cancelled for budgetary reasons.
Chicago's city flag features four stars which represent Fort Dearborn, the Great Chicago Fire in 1871, and their two world's fairs. If they'd won the right to host the 2012 Olympics, there were plans to add a fifth star.
Many of the items exhibited at the 1893 World's Columbian Exposition were put on a train and exhibited at the 1894 California Mid-Winter Exposition, the first of San Francisco's three world's fairs... so far!