There's also a large part of West Virginia where cell phone signals, WiFi, etc. are banned. They claim it's due to the telescope array located in the state, but perhaps there's more to the picture. I always thought it was odd that a "quiet zone" covered such a large swath of the east coast.
https://www.npr.org/sections/alltechconsidered/2013/10/08/218976699/enter-the-quiet-zone-where-cell-service-wi-fi-are-banned