Lake Van Norden 1950's - The case of the missing rock -
When the dam was in full operation, Lake Van Norden was pretty big. Not that deep, but long and wide. Boating was popular, and Norm Saylor even had a ski jump, visible in the old photo.
Also very prominent were the two large 8-foot-long rocks atop a volcanic pedestal. They are also visible in Alfred A Hart's photo from the 1860's (See "Summit Valley from Lava Bluff Hart 109" on the scenery page of Then and Nows).

Sometime in the last fifty years, one of the rocks disappeared. It's been suggested that someone used a bulldozer to dislodge it, but that would have been difficult due to the steepness of the pedestal.
The slope below this point is also very steep, and a search of the area didn't reveal the missing rock. Abducted by aliens? College prank? Who knows?

Photo location 39° 18.944'N 120° 22.935'W