Thread by @AtomicAnalyst

79 years ago this afternoon (3:25pm), in an abandoned squash court beneath the West Stand of Stagg Field @UChicago, a team led by physicist Enrico Fermi used a secretly-built reactor (Chicago Pile 1) to achieve the world’s first artificial, self-sustaining nuclear chain reaction.

Three scientists—Leona Marshall, Herbert Anderson, and William Sturm—recorded measurements that day in a log book as control rods were slowly removed in order to achieve criticality. See the notation “We’re cookin!” at 3:42:30 Central War Time at the bottom of page 29.

Metallurgical Laboratory head Prof. Arthur Holly Compton called James Conant, chair of the National Defense Research Committee, to share the news in ad hoc code:

Compton—“The Italian navigator has landed in the New World.”
Conant—“How were the natives?”
Compton—“Very friendly.”

To commemorate this historic but secret achievement and honor project director and Italian physicist Enrico Fermi, physicist Eugene Wigner produced and opened a bottle of Chianti Bertolli wine that everyone present silently drank from (using paper cups) and subsequently signed.

Ted Petry, the last of the 49 witnesses to this world-changing event, died in 2018. He was a 17-year-old high school student who worked as a laborer building the 20-foot-tall pile composed of tons of ultra-pure graphite, uranium metal, and uranium oxide.

Chicago Pile 1 led directly to the secret construction of the X-10 graphite reactor at Oak Ridge, Tennessee, and the B Reactor at Hanford, Washington. The latter produced plutonium for the first atomic bomb, detonated 957 days later southeast of Socorro in the New Mexico desert.

The original Stagg Field was demolished in 1957. The site was declared a national historic landmark in 1965. In 1967, on the 25th anniversary, a sculpture by Henry Moore was erected to commemorate that momentous day. It stands there still, next to two libraries and a dormitory.