ELI5: Explain Like I'm 5

California postmile

Imagine you are driving on a really long road in California. Along the side of the road, you might see these little signs with numbers and letters on them. Those signs are called California postmiles.

The numbers on the postmile signs tell you how far you are from a certain point on the road - usually the beginning or end of the road. For example, if the postmile sign says 27.3, that means you are 27.3 miles away from the starting point of the road.

The letters on the postmile signs can help you figure out which part of the road you are on. Different sections of the road might have different letters to help you know where you are.

So basically, California postmiles are helpful signs on the side of the road that tell you how far you are from the beginning or end of the road and which part of the road you are on.
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