The Office of Financial Management's Population Page provides the best state-produced population statistics.
2012 Population Trends covers cities and counties in Washington.
The Office of Financial Management offers the Washington State Population Survey, providing a profile of Washington residents.
Washington County Profiles give population, economic and employment information on most counties in the state.
Washington State Statistics from the U.S. Census, includes population and economic data from 1990 on.
The Northwest Income Indicators Project has county data from 1969-2011 on population, income and employment.
See also our Demographics Resources page.