This is a strange bit of disputed archaeology. Check it out over the web and Wikipedia does have a good description:
The Los Lunas Decalogue Stone is a large boulder on the side of Hidden Mountain, near Los Lunas, New Mexico, about 35 miles south of Albuquerque, that bears a very regular inscription carved into a flat panel. The stone is also known as the Los Lunas Mystery Stone or Commandment Rock. The inscription is interpreted to be an abridged version of the Decalogue or Ten Commandments in a form of Paleo-Hebrew. A letter group resembling the tetragrammaton YHWH, or “Yahweh,” makes four appearances. The stone is controversial in that some claim the inscription is Pre-Columbian, and therefore proof of early Semitic contact with the Americas.
The first recorded mention of the stone is in 1933, when professor Frank Hibben, an archaeologist from the University of New Mexico, saw it. Hibben was led to the stone by an unnamed guide who claimed to have found it as a boy in the 1880s. The 1880s date of discovery is important to those who believe that the stone was inscribed by a lost tribe of Israel. The Paleo-Hebrew script is practically identical to the Phoenician script, which was known at the time, thus not precluding the possibility of fraud. One argument against the stone’s antiquity is its apparent use of modern Hebrew punctuation, though amateur epigrapher Barry Fell argued that the punctuation is consistent with antiquity. Other researchers dismiss the inscription based on the numerous stylistic and grammatical errors that appear in the inscription.