I see U^235 and I relate an obscure fun fact: separating the isotopes of Uranium is an extremely difficult task because they behave identically in the chemical sense. One of the techniques developed by the Manhattan Project during WWII was electromagnetic separation. When a charged particle (or ion) moves through a magnetic field, it experiences a displacing force that is perpendicular to the direction of motion (which is pretty fucking strange in and of itself - imagine pushing an object on the floor and having the force of friction move it sideways instead of resisting your push).

This force perpendicular to the direction of motion causes the ion to travel a slightly curved path. The electromagnet separation technique involves creating a stream of ionized atoms of unrefined Uranium and firing it through a strong electromagnetic field; because the particles of U^238 and U^235 experience the same force during this, the U^235 ions, being slightly less massive, are displaced a bit more and so follow a slightly more curved path. By placing collectors at different positions, you end up with a small amount of U^235 and a large amount of U^238.

These giant electromagnets would normally have used copper wire for their windings, but copper was a strategically critical material for the war effort and was in very short supply. So the Manhattan Project basically checked out the United States' silver reserves and used that for the windings instead (silver is not quite as good as copper for this purpose but is obviously better than nothing).

The electromagnets also used a lot of electricity, and this is why the Uranium-refining facilities were located in Oak Ridge, Tennessee. FDR's WPA had built multiple dams around there during the 1930s, and their turbines were put to work generating electricity for the magnets (it was also used for the thermal and gaseous diffusion processes).

The Manhattan Project's price tag is famously given as a round number of $2 billion dollars (in 1940s dollars), but this estimate does not take into account the value of these silver reserves or the cost of the WPA projects which were so critical to its success. The silver costs are a bit of a weird accounting item since all the silver (minus a surprisingly small amount lost to wastage) was eventually returned to the Treasury, but the last of it in use wasn't returned until the 1970s.