In the past five years, no major county in the U.S. had a bigger personal income gain, percentage-wise, than Washington’s own Snohomish County.

Snohomish County had the biggest five-year upswing among major counties, boosting its total personal income by 40 percent. And King County is ninth in the U.S. with total personal income of more than $109 billion.

According to new American City Business Journals research, the residents of America’s 100 largest counties collectively earned a cool $5.86 trillion in 2009. That’s trillion with a T.

California’s Los Angeles County led the way with total personal income (TPI) of $402.46 billion, according to newly released figures from the U.S. Bureau of Economic Analysis.

The runners-up in total personal income were:

— Cook County, Ill. (Chicago) -- $244.06 billion

— Harris County, Texas (Houston) -- $196.78 billion

— New York County, N.Y., aka Manhattan -- $171.95 billion

— Orange County, Calif. (Los Angeles area) -- $148.37 billion

— Maricopa County, Ariz. (Phoenix) -- $142.01 billion

— San Diego County, Calif. -- $139.58 billion

— Dallas County, Texas -- $111.32 billion

— King County, Wash. (Seattle) -- $109.05 billion

— Santa Clara County, Calif. -- $99.55 billion

TPI is defined as the income received by all people from all sources in a given year. It covers everything from employment wages to Social Security and welfare payments. See the bottom of this story for an income database that encompasses 3,108 counties and independent cities.

The recession was at its height in 2009, pushing income totals downward in most parts of the country. Eighty-eight of the top 100 counties registered declines in TPI between ’08 and ’09.

The sharpest drops occurred in Oakland County, Mich., where total personal income dropped 8.1 percent in a year, and New York County, N.Y., where it fell 8.0 percent.

But the long-term picture was much brighter. All 100 counties experienced TPI growth between 2004 and 2009, with 22 counties increasing by more than 25 percent.

After Snohomish County at 40 percent, the District of Columbia, which is considered a county-level equivalent, was next with a gain of 38.9 percent.

New York County led the 100 biggest counties in per capita personal income, which is calculated by dividing TPI by total population. These were the five leaders:

— New York County, N.Y. — $86,607

— Fairfield County, Conn. — $65,087

— Morris County, N.J. — $61,012

— Westchester County, N.Y. — $59,445

— Fairfax County (combined with the independent cities of Fairfax City and Falls Church), Va. -- $59,184

After you click here, you’ll find each county’s total personal income and its per capita personal income. (A few counties have been excluded from the database because complete income data were unavailable.)