The National Radio Quiet Zone

Most of America is absolutely saturated with RF. Some engineers call it "the haze." Much like a fog, it obscures everything else. Signals bleed into each other, every electical device producing its own hum and buzz. This is literally almost everywhere in America... except for one 13,000 mile square in West Virginia.

The National Radio Quiet Zone (NRQZ) was established by the FCC and the Interdepartment Radio Advisory Committee (IRAC) in 1958. It's purpose was to minimize possible harmful interference to the National Radio Astronomy Observatory (NRAO) in Green Bank, WV and the radio receiving facilities for the United States Navy in nearby Sugar Grove, WV.

The NRQZ lies approximately at longitude 78d 30 W and 80d 30m W by and latitudes of 37d 30m N and 39d 15m N near the state border between Virginia and West Virginia. It encloses some of Americas least populous land including The George Washington national Forest, the Monongahela national Forest, the Allegheny Mountains and a whole lot of the Shenandoah Forest. (marked below in Green.)

Not many people live within the NRQZ, but those who do live by the rules of the zone.
This means, among other things, limited radio reception. Very limited. Radio stations must arrange their transmitters directionally away from the Green Bank telescope. Cell phone towers have been kept to a bare minimum. So no cell phones, no walkie talkies, garage door openers, pagers, wifi, iradio or iTrips. Even Cordless microphones are forbidden. Power lines must be buried 4 feet below ground here. At the center of the area even ordinary gas-powered engines are banned. (sparkplugs cause unwanted noise) The Observatory staff use a fleet of 1960s-vintage diesel cars and trucks.

[I mean everything. Even the North American flying squirrels tagged with telemetry transmitters by the US Fish & Wildlife Service are a problem.] Wired had a great article on this here.