This is a large propped boulder with a smaller propped boulder in front. From the other side, it looks like the boulder is pointing. The long axis of the larger rock was almost perfect N-S.
This large boulder has a prominent squarish mark that looks man-made on its west face. It is about eight inches tall. Immediately to the right of the hole in the bottom of the square mark is a large quartz crystal (arrow). The deep marks may have been created by someone gouging out quartz.
The bottom part of this mark is visible above and behind the smaller propped boulder.
This boulder, seen from the side opposite that shown 9/4/2013, also had N-S alignment of the long axis. The open space underneath has E-W orientation. Closer examination shows flat rocks that might have been pulled out from underneath the boulder when the open space was created.
On all these boulders, the long axis orientation was N-S. Since many of the other boulders on this hill have this orientation, the glaciers may have deposited them this way.
The propped boulders in the alignment (9/4/2013) definitely show some human working, especially this one at waypoint 1870.
The planes remaining when rock was removed are visible on the lower surface. Maybe the granite at the bottom of a boulder in contact with bedrock gets cracked from repeated exposure to freezing and thawing. The Natives found it easier to chip the granite from the bottom of the boulder, creating a propped effect.
Whenever I think I've seen everything in a site, something proves me wrong. I was wandering down the side of the hill on an unfamiliar path, and I saw this:
Closer examination shows it is a beautiful propped boulder, with the inverted triangle shape sometimes seen at this site.
Here's a view of the other side. The long axis was also N-S.
I imagine this area once looked like a sculpture garden when the Natives kept the forest thin. It is hard to believe that these structures were in full view for the centuries during which the area was farmed, and nobody noticed them.