County-Maintained Bridge, Viaduct, or Large Culvert
Alternate Views of the Map
The above map displays significant locations along County-maintained roads that have been assigned a postmile, including bridges, intersections, culverts, and changes in jurisdiction. NOTE: Roads that are within city limits, state highways, or private property do not belong to the County-Maintained Road System.
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.
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)