On page 355 of the book "Over North in Sierra County" by James J. Sinnott, there is a statement that one "Snowshoe Thompson" participated in the Third Snowshoe Races (1869) sponsored by the Alturas Snowshoe Club (club formed in 1867).

As time permits, I am currently creating a surname index for this book and am posting it at:
http://cagenweb.com/sierra/Ref_books/OverNorthIndex.html

Rick Hanson
Sierra County CAGenWeb