Hundreds of Years of Use

Saturday afternoon I went for a walk at one of my favorite sites.  A few years ago, I took this picture there:

Recently, I was reviewing these photos, and noticed that the stone in the bottom of the photo looked like it had a grinding slick on  top.  This site is a small hill overlooking a stream, and it was easy to find again.
Closer examination of the stone showed a grinding slick  in a symmetrical stone with a flat top.

Here it is with the leaves removed.

  If someone was using this grinding slick, she would face to the southwest.

Why face southwest?  There are two possible reasons that are not mutually exclusive.
     1.  The god Kantantowit came from the southwest, bringing corn.
     2.  The winter sun would keep this stone warmer.
This propped boulder with a grinding slick (9/18/2013 ) also faces southwest, and is only 500 feet away.

These stones were shaped for a practical use, and saw hundreds of years of use. Their location on small hills near water suggests they were once part of  campsites.