Mine works everywhere, you need to just pre-load the Google maps for your rural area before you lose the signal. Have used mine in Africa, where there was no signal for a couple of 100 miles. If you lose the signal for a short while, as long as your phone is not switched off, the maps will be loaded ahead far enough automatically to get you through in almost all cases here in the US. I don't even mount my Iphone, it is in my pocket with an extended battery charge pack and I listen to directions through wireless headset.
https://smartphones.gadgethacks.com/how-to/google-maps-101-download-maps-for-offline-use-0179273/