Where is CM79?

Each grid square is two horizontally adjacent square below, with boundaries on even numbered longitudinal lines:

CM79 contains only one 7.5" quad, and the amount of land area in miniscule:

 

Where is CN70?

CN70 is much larger and contains numerous 7.5" quads, but the map showing 15" quads is easier to make sense out of"

 

What about CM86?

CM86 contains about half of Santa Cruz and the tiny town of Davenport, but still includes an awful lot ocean.

Here's where i went last year:

Other suggestions welcomed.