The Washington Post has a map of the US showing when the median income in each county began to decline. If you move the cursor over a county, the statistics about that county appear on the right. The small maps across the top are the key to the color coding for when the median income began to drop in each county.
This is a screen shot taken with the cursor over Bernalillo County, New Mexico, where I live, where the median income peaked in 1999. That's when median income began to decline in the biggest number of counties in the US -- 1,623.
"Median" means half the population's incomes are above that amount, half are below.
The map is accompanied by an article that tells the story of how the median income peaked in Downy, CA, when it lost all of its aerospace industry jobs, but doesn't say why median incomes have dropped across the entire United States and gives no indication of the systemic changes to our economy that have caused it. That kind of information is promised in a next installment, but like a New York Times article about the increasing numbers of traditional "breadwinners" who have simply left the workforce it will probably blame the Great Recession and ignore the fact that the dramatic decline of the American worker's prospects date back to the late 1960s.
Below is the same map as above but showing statistics for Berrien County, Michigan, where I grew up. It's the dark spot in the extreme southwest of the state. The median income peaked there back in 1969, when what would come to be known of as Reaganomics was just getting started, when American Capitalism began to desert America and the attacks on unions began and the auto industry, centered around Detroit and Flint (see dark spots in the central and eastern parts of the state) began to decline, taking with it the steel making and auto parts industries (see dark spots along the southern edge of Lake Michigan and across northern Indiana, the state below Michigan, where many people in my town, New Buffalo, worked, as did I at one time, as did my father and my two brothers.)