We went to the Washington State History Museum today in Tacoma. This was our first visit. It's a surprisingly good museum; Andrew even proclaimed it was "better than Chuck E. Cheese" which, for him, is saying something. (I admit, this may have been because of the train exhibit where they let you play with Lego trains and Lincoln Log stuff.)
There exhibits where well done, covering Washington's relatively short history in reasonable detail with a good mix of reading, hands-on stuff, and multimedia. The museum is in the recently restored area of Tacoma near the Museum of Glass and the Tacoma Art Museum. The whole area is pretty cool, although it was empty today, despite being a beautiful Sunday. I imagine people in the area (like us) are still not used to hanging out in downtown Tacoma. I hope it improves. They've done a good job.
Anyway, we'll be going back again.