Petroglyphs
Hokan peoples left rock carvings, which can be construed as some of the earliest "written language" from the western part of North America. One form of the carvings was known as Pecked curvilinear nucleated, a notable example of which can be found on Ring Mountain, California. Although all of the symbols are not clearly translated, it is clear that considerable thought and effort went into the production of these carvings, many of which survive to the present day.
Read more about this topic: Hokan Languages