[Lucid:]

Most state nicknames are about the nature of the state, actually. They were made up so long ago that the culture would have changed beyond the state nickname otherwise. Most of the ones that aren't based on natural features of the state are based on history.
http://www.50states.com/nickname.htm#.VoV2NBUrKHs

The town in Washington I grew up in actually had quite a few leafy trees, too. Unsurprisingly, the town's name was Maple Valley. xD And of course there were also TOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOONS of evergreen trees in addition to the maple trees. It's such a beautiful area though.