Worlds Fairiana
I buy and sell a fair (hah!) amount of World's Fair collectibles. World's Fairs - also known as Expositions (Expos) - have been the showcases for introducing new inventions and products (including telephones, Dr. Pepper, the Ferris Wheel, waffle cones) and introducing far-flung cultures and nations and promoting humanitarian interests to fair visitors. I like it because it provides a glimpse into the past; you can see who presented themselves on the cutting edge, and see what the people of that time thought was wonderfully different and exotic and new, whether it was dancers from Bali, the thrill of a giant wheel you could ride, or the idea of an incubator to help babies survive.
The first international exposition took place in London in 1851 (Prince Albert organized it; his crystal palace became internationally famous), and continued in cities around the world every two to six years. This year, Shanghai will be hosting the World's Fair. In the past few decades, as the World's Fairs have become a platform for countries to launch and present themselves in their best light and technologies (satellite, internet, television, et al) have tied the world closer together, the nature of World's Fairs have changed and may be less collectible outside of their local regions.
Here in America, the big 3 World Fairs for collectibility are the 1933 Chicago World's Fair (A Century of Progress), 1939 New York Wold's Fair (with the iconic trylon and perisphere), and the 1964 New York Wold's Fair (with the iconic unisphere), with the 1904 St. Louis World's Fair (of Meet Me in St. Louis fame) and the 1876 Philadelphia Exposition (Centennial Exposition) following close behind. You can find a good array of souvenirs and artifacts from all five of these world fairs online and in shops.
Early World's Fairs in Buffalo (1901), Chicago (1893), New Orleans (1884), Jamestown (1907), Seattle (1909), and the Panama-Pacific/California (1915) are rarer in the market, particularly outside of their regions. Later Expositions in Seattle (1962), San Antonio (1968), Spokane, Knoxville (as depicted after the fact in a The Simpsons episode) and a number of Canadian cities are more common and more affordable.
The breadth of World's Fair souvenirs (and their value) is astonishing; I've sold mini models of the Unisphere and the Perisphere/Trylon combo, books and brochures, plates and pitchers and pottery, coins and spoons and packets of photographs. There have been souvenir portaits and salt and pepper pairs; bottle openers and glass decanters; stereoscopic Foto-Reels and stereo cards. That's just the tip of the iceberg!
People collect World's Fair stuff because they are home town enthusiasts, or because they visited the fair as a child; they collect because they love the style and decoration associated with the fair, or the wonder and whimsy introduced there. Sometimes they collect because it's cobranded with a commercial brand (e.g. White House made World's Fair vessels for their vinegars and juices; Planters famously placed Mr. Peanut and the World's Fair icons on a nut snack set), or because the fair had a fabulous exhibit or pavilion associated with another collection, including railroadiana, made in japan ceramics, and photographic equipment.