Bitcoin may seem to have suddenly appeared out of nowhere in 2009. In fact, it is only the best-known recent experiment in a long line of similar efforts going back to the 1970s, as technological utopians and political radicals tried to create new currencies to bring about their visions of the future -- whether saving privacy, destroying governments, preparing for apocalypse, or attaining immortality. This talk will take us from autonomous zones in international waters, to the finances of freezing humans for future revival, to the challenge of securing analog dollars and coins, and explore questions like: How do we learn to trust and transact different kinds of money? What makes digital objects valuable? What would it take to make a digital equivalent to cash, something that could be exchanged but not copied, created but not forged, which reveals nothing about its users?