Measures 22 x 26.5" 2 sided printing , one side covers Bel Marin Keys area, the other Pt Reyes, Drake's Estero and the National Shoreline . Drainage, flow and tides are indicated in this series of technical maps , they were used relating to development and flooding within the county. Produced by the Dept of the Interior for such purposes . From an SF based engineering firm archive , now divested .