Harbor Oil Refining Company Gas Station Road Maps of California
Harbor Refining Company - California Road Maps
Harbor Refining Company - California Road Maps - Front
Harbor Refining Company - California Road Maps - Back
I really don't know how many different years Harbor Refining produced maps, but the above is a good representation of their maps. The map in the bottom row appears to be from the 1920's.
The following clickable link will open a Check-List type Spreadsheet that will include Map Codes, Copyright Dates and other descriptive information for the above pictured map series.