I went to http://searches.rootsweb.com
, which is a great beginning search page, then to California and then to Death. After entering the name, I found William DWYER who matched your information and died in BUTTE County. The results of my search are at http://vitals.rootsweb.com/ca/death/search.cgi
There are other links you could search at rootsweb such as Social Security Death index etc. Give it a try.