I-502 passed in Washington State's 2012 election with 55% of the vote, legalizing mariijuana in Washington State. Washington was one of two states that legalized pot not just for medical use, but for recreational use, too--the other being Colorado.
The issue isn't as clean cut as it might seem, though. Marijuana is still illegal federally, which might make implementation a little tricky. The state also doesn't have a weed infrastructure set up yet and isn't required to have the full system up and running until December 2013. So the next year will be filled with new specifications and new details emerging on how exactly this will work.
In the meantime, there are already changes afoot--Pierce and King counties are both dropping many marijuana misdemenor charges