The Center for Economic Development at Chico State University in Chico, California has compiled a fairly comprehensive report of regional demographics. Please check out this report for recent detailed statistics on Siskiyou County population, labor force, unemployment, income, earnings, revenue, cause of death, etc.
The following table, Population by City, is not part of the above mentioned report and may be of interest to some individuals.
Siskiyou County Population by City, 2011
Source: CA Department of Finance Website