GPS is great if you have an address to navigate to; however, in some places in California, there are no nearby major landmarks, no street signs, and the location you’re trying to find lacks a formal address.

So what do you do then? Look to the mileage markers, also known as postmiles. They’re one of those helpful signs you might not notice until you need them—white rectangular signs that you may have never seen standing alongside the road. After you read about them below, you’ll know how to use them when you need assistance.

Mile markers are not to be confused with exit numbers. Both mark your location on a road; however, exits are numbered continuously from border to border. In contrast, mile markers are more local, resetting every time you cross a county line.

Where to Find California Mileage Markers

These markers can be found on state and county highways, but not on the Interstate or US roads. Look for them at the roadside, sometimes at the end of a guard rail. They are not evenly distributed and can sometimes be extremely close together or far apart for no apparent reason.

You may also find postmiles on bridge overpasses, providing the same information as the postmile sign along with the bridge number. For example, “405 LA 32.46” signifies I-405 in Los Angeles County at mile 32.46.

If you happen to see a roadside call box, the postmile may also be coded into its number. Unfortunately, counties vary in how they do this. For instance, a fictitious call box 103-402 would be near mile 40 of Highway 103, with the final number signifying it’s the second box within that mile.

What California Mileage Markers are Good For

California didn’t invent mileage markers. In fact, it was the last state in the country to adopt mile markers, only beginning to implement highway exit numbers in 2002.

To make navigation easier in areas lacking landmarks and signposts, directions for remote locations in California often list the nearest highway mileage marker.

They are essential for navigation; you could provide their number to emergency road services, informing them exactly where your broken-down vehicle is located. Furthermore, local governments use these markers to help keep track of precise locations along their roads.

If you are directionally challenged and don’t have a compass in your car or on your mobile device, you can use mile markers to determine your travel direction somewhat. If the mile numbers are increasing, you are heading east or north.

How to Read a California Mileage Marker

For east-west roads, mile 0 is found on the western end, with numbers increasing as you travel east. Conversely, for north-south routes, mile 0 is at the southern end, with numbers increasing as you head north. Numbering restarts each time you cross a county line.

Here’s how to interpret them, using a typical example:

• The number at the top of the sign is the highway number, such as CA Hwy 1.
• The letters indicate the county; for instance, MON designates Monterey County.
• The numbers indicate the mile it marks, such as mile 58.

Reading the sign from top to bottom makes it clear that the photographer was standing on California Highway One in Monterey County, 58 miles north of the county line.

Unlike mileage markers in some other states, California markers are numbered in the same sequence in both directions. Thus, if you looked at the marker just opposite on the other side of the road, it would be marked identically.

California Mileage Markers and Google Maps

Google Maps generally ignore mile markers; they aren’t used in navigation and are absent from map view. The only opportunity to spot one is to access street view and drop Pegman (the little cartoon figure) onto a street, then look for a mile marker by the road.

To test this, search Google Maps for Pfeiffer Canyon Bridge in California. Drop Pegman north of where Sycamore Canyon Road is located and face him south. Zoom in near the side road to see mile marker 45.64, which is a notable landmark relevant for navigation.