Asset Overview
Walter Cooper is buried in the same plot as Alice Maria Paxton Cooper (https://sketchfab.com/models/5a98051aae9740828a5fe967418a9b7a). The Sacramento County Archives list him as being 31 at the time of his death, but a record in the New England Historical and Genealogical Register of 1896 indicates that his tombstone said "32". Either way, since he died in 1870, that would put his birth year at roughly 1838-1839.
It seems, based on accounts of his having built a saloon in Felton and leased a property in Felton to one Mr. McCoy, as though Mr. Cooper was involved in real estate. His business partner was J. M. Merrill.
http://www.feltonfire.com/pictures/feltonhistory.html
https://books.google.com/books?id=FA8ALY0ZtYYC&pg=PA440&lpg=PA440&dq=walter+cooper+santa+cruz+1870&source=bl&ots=buEsM3UM1u&sig=FZKU-7kKaAjcoU9dQYUMwkpoI3k&hl=en&sa=X&ei=aI1oVf6ICcGtogTat4KgDg&ved=0CCsQ6AEwAg#v=onepage&q=walter%20cooper%20santa%20cruz%201870&f=false
http://files.usgwarchives.net/ca/sacramento/newspapers/sacramen19nw.txt