Letterbox #1: Mortar Rock

For more information and stories related to this letterbox, see the following pages under S.F. Bay History: The Ohlones.

This letterbox is hidden in Mortar Rock Park in North Berkeley, at 901 Indian Rock Avenue near the intersection with San Diego Road.  The large granite outcroppings contain several acorn grinding pits formed by Ohlone women grinding acorns in the same spots for centuries.

The clues:  Start at the 8 stone steps next to the “Mortar Rock” informational plaque on the NW side of the park.  Climb the 8 steps, then veer left and go up 3 more stone steps.  Continue up the pathway, passing under Buckeye trees.  When the pathway levels out continue straight, walking past a larger (approx. 10 ft hight) boulder on your left.  Just beyond that boulder, on you right, you will see two low mossy rocks with acorn grinding pits worn into them.  When you pass the second of these rocks (with 2 deep grinding pits), take the path that veers right.  This will lead you to another stone with 2 more deep grinding pits.  Pass to the left of that stone and then go up the three stone steps to your right.  In front of you is a tight cluster of Bay trees.  Keeping these trees to your left, circle around to the back of the cluster, away from the street.  Search in the center of the cluster to find the letterbox!

When you find the letterbox, read passage copied onto the first page of the notebook inside.  It’s from a book entitled  “The Ohlone Way” by Malcolm Margolin.  Or better yet, buy a copy of the book or check it out from the library,carry it with you, and read aloud the 4-page chapter on the Acorn Harvest.  Can you imagine the sound of pounding mortars?

Please be sure to replace everything in the letterbox, seal the lid carefully, and hide the  box well in the same spot where you found it.  Enjoy!

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