Decorating your wooden or standard derricks in the early 1900's with signs of your company, or the name of your well, appears to be sort of a California thing. I suspect this was partially due to the shear number of wells in urban areas like Huntington Beach, Signal Hill, Wilmington or Santa Fe Springs and the need to know who's was whose.
Take the photo above, for instance...try giving directions to a dumb ass truck driver at the soap, rope and dope store to your well... located in that neighborhood. What do you say? Turn left at the boiler making steam and we're on the right, next to rig with galvanized tin wrapped around the floor? Signs at least helped get your stuff delivered to the right place.
Lots of times in California you could probably give directions to somebody by simply saying we're two rigs upwind from the sumbitch on fire and that would work pretty well. You might have to clarify that sometimes by saying something like... no damn it, not that one blowing oil everywhere, the one ON fire; what's the matter with you hand, can't you follow directions?
All these damn wells look exactly alike, they need signs, for sure. I think those are homes tucked in between rigs so maybe these wells actually had street addresses...
You could probably tell the hand delivering your pipe that this well, above, was on the beach, next to the lifeguard stand. That might work.
You'd think any worm delivering drilling mud could find this well, and it wouldn't need a sign, but if you do you haven't been in the oil business very long. I've known some hands that if you told them to go straight at the Y, they'd get confused and turn around. Imagine not being able to find THIS location. It happens, trust me.
Rig signs were also important for when you had guests come out. All these folks dressed up probably own 1% working interest in this well and came out on a Sunday afternoon for hot dogs and grape sodas to look at their investment. How painful it must have been to count 117 people at the rig party, all with 1% interest in the well. That ain't good, no sir. That well is going to have to a be a dry hole.
As an operator you would want to have these kinds of shindigs occur before the well comes in blowing shit everywhere getting peoples Sunday-go-to-church-clothes all nasty.
And if you were drilling a tight hole and didn't want people snooping around your location you could use a sign like this on the back of your dog house to scare 'em off. Works for me !