You nailed it! Walnut Grove is a little town along the waterway between San Francisco and Sacramento. IIRC, the town has about 10 buildings, and a few bait shops on the main road that runs by the waterway.
They also have some nice TV transmitter towers that you can see from I-5! (Sacramento market).
https://www.fybush.com/sites/2005/site-051111.html
“Downtown”: https://goo.gl/maps/bwtuckeVHku