Coming up...70 year anniversary...first self-sustaining, controlled nuclear chain reaction

On December 2, 1942, 49 scientists, led by Enrico Fermi, made history when Chicago Pile 1 (CP-1) went critical and produced the world's first self-sustaining, controlled nuclear chain reaction.
  
Read the story at Argonne National Laboratory's website.

And...

Historical event in 1942 at the University of Chicago