The material was at Mather AFB when the war was called off.
Which would have been Mather Army Air Field at the time. During the summer of 1945, the 509th Composite Group was transferring from its Second Air Force training base at Wendover Army Air Field, Utah, the group landed at Mather prior to embarking on its trans-Pacific movement to Tinian (in the Marianas Island chain). Due to the extraordinary security of the unit because of its atomic mission, the commanding general of Mather Field was told at gunpoint that he was not allowed on board the B-29 The Great Artiste, which had landed there.