Postmile System


Bridge 3

County-Maintained Bridge, Viaduct, or Large Culvert

County Maintained Road

County-Maintained Road

Alternate Views of the Map

Map Information

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.

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)

Contact Information

Business Hours
Monday – Friday
8:00 AM – 5:00 PM
Contact us by Phone
Office Location
La Plaza B
2300 County Center Drive
Suite B 100
Santa Rosa, CA 95403
38.462023, -122.725381

Interactive Maps

Sonoma County Interactive Maps


Thematic interactive maps for Sonoma County