Back in the 50s when lots of folks lived in small town America the local High School kids would put the letters up on the nearest hill - sort of a school spirit thing. I think they just lasted longer in Nevada because they don't get overgrown or overcome by growth. It may have been a Western States thing - you do need a hill or a mountain to do it. I know several of the little towns in Northern California, where I grew up, had them. The only time I've seen a full name was Silver Springs - about 30 miles out of Carson City - and it was painted on the water tower - more of a mid-west thing.