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.)
Legend
 |
Bridge |  |
State or US Highway |  |
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.