This is my favorite plaque in Olympia (and there are plenty to pick from).
I think that plaques are entirely underrated. Behind every plaque is immense effort made by someone or some group that thought some event was important enough to be commemorated.
This plaque happened to be placed by the Sacajawea Chapter Daughters of the American Revolution in Olympia (you see I know this since it's on the plaque--brilliant!).