1. Alaska
2. Washington
3. Oregon
4. Nevada
5. Colorado
6. Massachusetts
7. Maine
---Non States
8. Washington DC
9. Our neighbors to the north. Canada.But in DC, marijuana sales are still illegal, which makes for an interesting situation: you're allowed to be in possession of something you cannot legally buy.
The Netherlands has a similarly bizarre circumstance where it's perfectly fine (though technically illegal) to buy <5g in a shop but it's still quite illegal for that shop to be supplied with product, as commercial production is illegal and heavily counteracted by law enforcement.
Recreational use isn't legal here (though enforcement varies, depending on where you are). Medical use has been for a while. The current government is likely to table legislation sometime next year, but no one knows yet what form it will take.
The next administration may take a different approach to enforcement than the current one (I think it is kind of likely. But let's hope they choose not to prosecute growers and dispensaries and such.)