At the high point itself, the Northwest Airlines corporation placed this marker in the late '50s to commemorate the "adventurous spirit" of their pilots and navigators. A government-issued notebook was stored in a metal box underneath this monument, in which you could record your name and your impressions of the journey up the mountain.
Note the bird flying in the sky beyond the monument. These "swifts" would fly around so fast that they'd make a zipping noise through the air. Every time I heard one, I thought that it was a mountain lion coming to get me.