The task of creating a Palace of Fine Arts for the 1915 Panama-Pacific International Exposition fell to the architect Bernard R. Maybeck. Setting to work on this new project, he chose as his theme a Roman ruin, mutilated and overgrown, in the mood of a Piranesi engraving.
By the closing of the Exposition, on December 4 of the same year, a movement to preserve the Palace was already under way; signatures and money were gathered from the Fine Arts League. But before a restoration could take place, the Palace many different uses. In 1934, eighteen lighted tennis courts were installed and remained there for eight years. During this period, the Palace, without proper maintenance and as a result of vandalism, was gradually crumbling into a genuine ruin. Then during World War II it was requisitioned by the Army for storage of trucks and jeeps. At the end of the war, when the United Nations was created in San Francisco, limousines used by the world's statesmen came from a motor pool there.
In the meantime, from 1947 on, the hall continued to be put to various uses: as a city Park Department warehouse; as a telephone book distribution center; as a flag and tent storage depot; and even as temporary Fire Department headquarters.
The work of demolition and reconstruction began in 1964. The rotunda and the columns were toppled to the ground. Nothing was left but the steel structure of the gallery itself.
By 1966, when 20,000 people visited the unfinished Palace during a public "walk-through," the new structure was close to completion. It had been solidly rebuilt by the best engineers available, the "staff" work being cast, stratified in the casting like stone, and proof against peeling off. A final solution for it's use was presented and in August of 1969, the Park and Recreation Commission formally approved the plan to house a museum.
Starting with a few temporary exhibits, the museum grew rapidly. In 1980, cramped for space by its collection of exhibits, the museum built a mezzanine within the exhibition hall, adding another 15,000 square feet of exhibit space. By 1983, the Exploratorium had more than 500 exhibits on light and color, sound and music, patterns of motion, language, and other natural phenomena.
Over the past decade, Exploratorium has greatly expanded its role in exhibit-based public education, becoming a nucleus for interaction between science, science education, and the public.
The entire history and information can be found here: