County Route Mile Posts

In general, if a stretch of county-maintained highway crosses into a
second county, does it retain its numbering or does it restart from
0?

I ask because the Salome highway, exit 81 on I-10 to Salome, has mile
posts, so it should be at least a county-maintained road. It runs from
Maricopa county to La Paz county without a discontinuity in numbering,
but it is not on any state route maps as far as I can tell. At any
rate, highways that go in between states lose their numbering so I
don't think it would be too unreasonable for county routes to reset
either.

Jason

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