Ciro Santilli This is where they moved the Chicago Pile-1 after they decided it might be a bad idea to run highly experimental nuclear reactions right in the middle of one of the most populous cities of the United States.
After it was reassembled, the Chicago Pile-1 was renamed as Chicago Pile 2 (CP2).
So more precisely, it is a continuation of the Metallurgical Laboratory.
It's still not that far though, only about 20 kilometers, and today is also a populated area.
Ciro Santilli maintains that they chose the site because the name is so cool. Wikipedia says it is derived from the Forest of Argonne, maybe it even shared etymology with the element argon.