Anyone in Seattle knows the Space Needle, downtown monorail and a few other things were built for the 1962 World's Fair. The World's Fair is an extravagant event that throughout history has left several major cities across the US with large, oddly-shaped landmarks and a legacy to tell to children for generations.
Asking around, I'd not been able to find anyone who has the slightest recollection of any World's Fairs since the early 1980s. It turns out that since Vancouver, BC in 1986, all subsequent fairs have been in other parts of the world. The World's Fair Museum site at expomuseum.com has the full details.
A trip to Shanghai in 2010 does sound rather tempting.