Once a upon a time
Gold was the medium of exchange, the one thing of value that could be hoarded for wealth. We put a huge amount of gold in Fort Knox which is the backup or foundation for all the paper money floating around. Although, as I understand it, we no longer have enough gold in Fort Knox to back up all our currency. This is just from memory and I could be wrong about some of it. Haven't looked it up. I could but I'm tired and won't tonight. I might tomorrow if I remember it.