There are two "Radio Quiet Zones" in the United States, the largest, the National Radio Quiet Zone (NRQZ), was created in 1958, and is located primarily in rural West Virginia and Virginia as shown on the map below. The other, Table Mountain, is located twenty miles north of Boulder, Colorado. If you're looking for a place to disconnect yourself from the world, these would make good choices as any source of radio transmissions is severely limited to allow for government surveillance and research. That pretty much means no cellular service and the closer you get to the center of the facilities, the more restricted it gets. For example, near the center of NRQZ, gasoline-powered cars are prohibited, as their spark plugs generate radio interference, so only diesel-powered engines are allowed. Read more at the link below.
Another shout-out to my buddy Nick for this tip!