I'm wondering what town is about half way there

Here's another site that shows you a whole bunch of towns along the route. You can use the percentage to find some possibilities close to 50% of the way, like maybe Cortena (California):
https://citiesbetween.com/yreka-ca-and-carmel-ca

If you use the 'directions' option in googlemaps it's easy to see which towns are roughly halfway on any journey, though it depends to some extent on whether you mean halfway by distance or halfway by driving time. 
To me, Willows or possibly Arbuckle (California) look roughly halfway between Yreka and Carmel By the Sea