When was XXX found or made?
Plutonium
Plutonium (specifically, plutonium-238) was first produced and isolated on December 14, 1940, and chemically identified on February 23, 1941, by Glenn T. Seaborg, Edwin McMillan, Joseph W. Kennedy, and Arthur Wahl by deuteron bombardment of uranium in the 60-inch (150 cm) cyclotron at the Berkeley Radiation Laboratory at the University of California, Berkeley.
1941