Research the name in your county records. Check mining locations, land deeds, homestead filings, etc. Since the name is not Hispanic, chances are there may be results if you're dilligent. [Many Hispanics during this time period were not in the public record]
Check your local historical sources. Many local groups, museums, libraries, etc. have rosters of former residents, newspaper histories, etc. This name is unusual and should be easy to track. If you or a friend has an Ancestry.com subscription, you can research the name there in the census records and other sources. If you can identify the man, you may be able to figure out why he was in the vicinity of the carving.
Jacob may have simply carved his name on this prominent rock for his own amusement - not an uncommon deed in the early 20th century west. Is the rock on a trail? Maybe Jacob died on the date indicated and was buried nearby. Is the area remote?
It would be peachy to assume this is a treasure sign, but you have no reason to get excited yet. 99+% of man made signs found (carvings, cairns, blazes, etc.) have nothing to do with treasure, but have other explanations. If you find out Jacob was a train robber, then you may be onto something. Do your due dilligence.