Yeah, I have seen it too.
The "MurphyHP" was a GREAT network and nearly EVERYWHERE in the Plains, especially W Kansas, Nebraska, and Colorado. Someone told me it might be a railroad based network for data-transfer / signal control for train operations or tracks.
Someone also told me some trains (such as Amtrack) offer free internet to travelers, I cannot verify this but I suspect that may be some interface with such a network such as "MurphyHP". I do not know anything more about this network. I saw "Linksys" coming up a lot too as a peer-to-peer network also (MurphyHP was also peer-to-peer).