It’s a rather strange thing really but I’d already done the idea for this sculpture before Professor McNeill and his colleagues from the University of Chicago came to see me on Sunday morning to tell me about the whole proposition. They told me (which I’d only vaguely known) that Fermi, the Italian nuclear physicist, started or really made the first successful controlled nuclear fission in a temporary building. I think it was a squash court - a wooden building - which from the outside looked entirely unlike where a thing of such an important nature might take place. But this experiment was carried on in secret and it meant that by being successful Man was able to control this huge force for peaceful purposes as well as destructive ones. They came to me to tell me that they thought where such an important event in history took place ought to be marked and they wondered whether I would do a sculpture which would stand on the spot. (Henry Moore quoted in Art Journal, New York, spring 1973, p.286)
The sculpture is described as 14.0 feet (4.3 m) in height and 8 feet (2.4 m) in diameter by the Smithsonian Institution, and it sits atop a base that is 1.5 feet (0.46 m) in height and 10 feet (3.0 m) in diameter. However, the University of Chicago says it is only 12 feet (3.7 m) in height. The Henry Moore Foundation lists its height at 3.66m. The sculpture reminds some of the human skull, while it reminds others of an atomic mushroom cloud.
The sculpture was erected for and dedicated at the celebration of the 25th anniversary of the initiation of the first self-sustaining controlled nuclear reaction on the grounds by Fermi on December 2, 1942. Thus, it was dedicated at precisely 3:36 p.m. on December 2, 1967. The site of the first nuclear reaction received designation as a National Historic Landmark on February 18, 1965 and was added to the newly created National Register of Historic Places (NRHP) on October 15, 1966 as one of the original designated historic places. Chicago Pile-1 is one of four Chicago NRHPs on the original list. The site was named a Chicago Landmark on October 27, 1971.