Well, you could do what the statehood quarters did back starting in 1998 or so. A series of legal, United States quarters were minted each with a different state illustration on the back. They were really cool – I have a collection of all of them in a little coin book. Each state held a competition asking locals to submit designs (at least my state did), then opened it up for a vote to everyone (even non-residents). I know that’s not quite what @Nullo is suggesting, but it’s a compromise. After all, @iamthemob‘s point is totally valid – it just confuses things. If each state made its own currency but that currency was acceptable anywhere in the country, then that would be fine, but once you get into the business of exchange rates and not being able to spend California currency in Colorado, we have a problem.