The World's Columbian Exposition of 1893 introduced picture postcards to the American public. Here is a postcard from that Expo... a genuine pioneer era postcard. The Expo showcased the power of the coming (20th) century, electricity, and the Fair also introduced carbonated beverages and hamburgers. A young Scott Joplin worked there, honing his Ragtime skills.
A wildly successful Expo, in my opinion.