It was first organised in 1930 by Abraham de Stark (Howard's father) to convince the Atlantans of their country's technological superiority after the Great Crisis. The first festival lasted six months and during that one scientists, inventors, manufacturers, and artisans of all castes were encouraged to present their discoveries and prototypes.
A decade later, in 1940, Howard de Stark decided the expo was an optimal way to boost Atlantans' morale during he World War and planned it as future regular event that would allow both him and his compatriots to show off and amaze foreigners. After Howard and Maria de Starks' deaths, Anthony de Stark shelved the concept, only to re-establish the Stark Expo in 2010.
The new Stark Expo was set to last a year. It was intended to allow everyone to show their achievements, not only scientific or technological, but also artistic. Of course, both Tony's and Stark-Carbonell Industries' inventions took prominent places, but the idea of the Expo was to encourage the exchange of ideas an establish new connections. Behind the scenes, it was Tony's way to directly steer Atlantis's progress around the Ton by the way of either sponsoring or sinking new inventions.
1940: Modern Marvels of Tomorrow organised by Howard de Stark
1950: 2nd Stark Expo
1960: 3rd Stark Expo
1970: 4th Stark Expo
1980: 5th Stark Expo
1990: 6th Stark Expo, cancelled by Anthony de Stark
2010: New Stark Expo organised by Anthony de Stark and Pepper de Potts de Familia Stark