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Postmile System

The Postmile Book

The Sonoma County Postmile Book is a comprehensive listing of significant locations along County-maintained roads (e.g. intersections, bridges, city limits, etc.)

View/Download the Sonoma County Postmile Book (PDF)

Postmile System Map

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Bridge 4 Bridge MiC2 State or US Highway County Maintained Road County-Maintained

What is a postmile?

A postmile (AKA post mile) is a numerical value that identifies a specific linear location along a County road, based on its distance (in miles) from the beginning of the road (e.g. if you are at postmile 10.00, then postmile 11.00 is one mile up the road). All Sonoma County roads have designated beginning and ending post mile assignments.