Thanks everyone for the comments.
A few years ago the city of Oceanside, CA renovated the area north and south of the pier and the beaches there. They built a number of public restrooms, including two on the beach. One at "Breakwater Way" and the Strand (the road along the beach) and the other at "Sportfisher" St.
This "Monolith" is a short "modesty wall" on one side of the restroom building at Breakwater Way.
The building at Sportfisher has a similar treatment with that name embossed there.
I'm impressed that the city planners had the inspiration to place the (otherwise) mundane identification of these municipal structures in such an artistic way and to commission the lettering treatment as embossing during the concrete pour, turning perfunctory concrete slabs into eye-catching objects.
Rich