The median income of Island County residents was an inflation-adjusted $30,980 per year. Island County had 34,027 households in 2017, with a population of 80,323.
The county with the highest median resident income in the state was King County. King County's median income was $40,852 per year after adjusting for inflation – $9,872 more than Island County. It had 851,077 households in 2017 and a population of 2,118,119.
Whitman County had the lowest annual resident income among counties in Washington, with a median income of only $16,042 per year. That was $14,938 less than the median income in Island County at the time. Whitman County had 17,657 households in 2017 and a population of 47,794.
The table below shows the state's counties ranked by median annual resident earnings in 2017.