The first human-made nuclear chain reaction.
Video 1.
Getting funding for the Chicago Pile Edward Teller interview by Web of Stories (1996)
. Source.
Video 2.
German graphite from The Genius Behind the Bomb (1992)
. Source. Graphite was expensive because it had to be boron-free, since boron absorbs neutrons. But a boron process was the main way to make graphite. This type of pure graphite is known as nuclear graphite.
The lab that made Chicago Pile-1, located in the University of Chicago. Metallurgical in this context basically as in "working with the metals uranium and plutonium".
Given their experience, they also designed the important X-10 Graphite Reactor and the B Reactor which were built in other locations.