The Hole-in-the-Floor Gold Heist was perpetrated by Mickey Malone and his gang in 1931.
Mickey Malone's gang crawled into a train through a hole they probably paid someone to create and then dropped 20 gold bars through the hole onto the tracks as the train was moving. More of Mickey's men were waiting to quickly collect the gold as it was dropped. In total, the collection is over 600 pounds. Mickey hid the gold at the bottom of his well at his cabin. When he was arrested, he tried to give William Akers, his right hand man, clues on how to find it, but he could never figure it out. It remained undiscovered until 2002 when Nancy Drew found it.