"Oak Ridge, Tennessee; Hanford, Washington; and Los Alamos, New Mexico"

They couldn't get access to the original site at the University of Chicago and Soldier Field, of course.

It's interesting that nuclear weapons have been re-invented about ten times in various nations around the world, sometimes just with public information and sometimes with American materials and instructions. Still, the original Manhattan Project is the fastest and cheapest of all the successful efforts to build a bomb. That's the value of hiring the best people in the world in your field.