Pay no attention to these signs

OK, it's probably not a conspiracy--no, really--but what's the deal with those displays that fraternal organizations put up at the outskirts of town? You're driving into some city, and suddenly there's a clump of little signs put up by Elks, Lions, Rotarians, Kiwanis, Knights of Columbus, Shriners, Masons, Illuminati, God knows who--it's hard to read the signs at 55 miles per hour. What's going on? Why are these signs at city limits? Are they the remnant of some weird medieval practice? Do the Optimists own my town? And what, exactly, are all these organizations for?

I wanted to link to an image of one of these collections of signs, but I CAN'T FIND ANY SUCH IMAGE ON THE WEB (!?!?!?!?!?!?!?!).

I got to thinking about all this because yesterday I was listening to Ray Stevens' classic novelty recording, "Shriner's Convention."