In a tributary of the Purgatoire (Picketwire) river in southeastern Colorado there is a vertical stone column with petroglyphs carved into its face. It was erected in a crude circle of large boulders. My photographs make it look like it is leaning on the rock behind it but, in fact, it is free-standing and not touching that rock with an unknown length of the column buried in the ground. The obelisk now stands approximately four feet tall but the top has been obviously broken off so it once stood taller, and probably sported more petroglyphs as well. About 20 years ago a chunk of the broken-off portion could be found lying at the base of the remaining column but whether it is still there or has been taken I cannot say. When that portion was added to the standing column the broken faces did not match suggesting that there was once still more column that is no longer in place. Back then we estimated that if the missing portions were replaced it would have stood around six feet tall, but that was largely guesswork.
This obelisk was erected inside a crude circle of large boulders suggestive of a shrine or sanctuary. Whether this circle was created, or naturally existed before the obelisk was added is unknown and no archaeological investigation has yet been attempted to my knowledge. The petroglyphs are abstract, and by the depth of the pecking and their repatination they appear to be archaic in age. That is apparent in the comparison of the color of the pecked lines to the coloration of the broken face at the top of the column. This is the only such example that I personally know of in North America. In the almost total absence of factual information it is tempting to see this as some sort of shrine or monument. In any event, it was purposely created and its very existence implies a great significance to its makers.
A book with a great deal of material on the rock art of southeastern Colorado and the Purgatory canyon is The Petroglyphs of Southeast Colorado and the Oklahoma Panhandle by Bill McGlone, Ted Barker, and Phil Leonard.