There are former Long Lines sites around the country, from urban high-rises to lonely fenced-in microwave horn antennas atop bunkers, miles from the nearest towns and sometimes accessible only by helicopter. A good few are next to highways and train tracks, which is how I came to start reading about them.
They provided rural telephony for civilians, but were also part of the Cold War-era continuity-of-government system connecting SAC bases and missile silos.
There's a fairly dedicated hobbyist community cataloguing the sites [0]. A remote Long Lines site also played a role in the Death Valley Germans story, which got some pretty good discussion on HN a while ago [1].
[0] http://long-lines.net/places-routes/
[1] http://www.otherhand.org/home-page/search-and-rescue/the-hun...