From the mid-nineteenth century on, expositions helped physically create urban environments, bring together spectacles and achievements, and communicate significant new developments to attendees and the public more broadly.
The expos were often held to commemorate important events. In the antebellum era, displays of national unity were necessary for healing. The Philadelphia Centennial Exposition of 1876 is a perfect example. While looking back to America's independence, it also highlighted industrial achievements.
The 1893 World's Columbian Exposition, often known as the Chicago World's Fair, was the largest scale expo to date. Ostensibly celebrating 400 years since Columbus's arrival, it brought speakers and performers from throughout the Americas. But even more, it celebrated Chicago itself as a gateway to the western frontier. Educational exhibits and speeches were a major part, and commemorative publications shared the knowledge with the wider public who could not attend.
For the 1904 St. Louis fair, for the centennial of the Louisiana Purchase, the architects and planners tried out a novelty: the entire grounds were fitted with electric lights, the first time a large urban area had been specifically set up that way. "Exotic" cultural groups were brought to live there and perform, such as the Igorot headhunters from the Philippines and Ota Benga, a pygmy from southern Africa who later went to live in the Bronx, New York zoo.
Tragic events occurred as well. President McKinley, appearing at the 1901 Buffalo, New York expo, was assassinated there.