Kansas City, St. Louis and and Baltimore are missing holes on a map of American prosperity. They are relatively low-income, encircled by wealth. Cross their county lines into the suburbs, and households there make, in many cases, nearly twice as much.

Same with Detroit, Philadelphia, Cleveland and Dallas.

The pattern is a classic American one, built through decades of postwar wealthy flight to the suburbs and disinvestment in cities. But it's striking today how deeply entrenched this geometry remains at the county level, especially in an era when poverty is expanding into the suburbs and wealthier households are moving back in.

Map median household income by county as we have above with new Census data — showing every county with more than 65,000 people — and, over and over again, you get a similar pattern. There's a lot of money in the suburbs, and a shortage of it in the city center:

In Baltimore City, for instance, the median household income in 2014 was $42,665, according to American Community Survey estimates released this week. The median income in suburban Anne Arundel County nearby is nearly $45,000 a year more. The income gap between Philadelphia County and Bucks County next door is $40,000, reflecting the much higher poverty rates in many central cities.

These maps also reveal a larger national pattern: Among the top 25 highest-earning counties in the U.S., every one of them lies outside a major city.

San Francisco County finally breaks that pattern, at No. 37. The median income in Manhattan (New York County) comes in at No. 70.

The four wealthiest counties on that map are all in the suburban D.C. region: Loudoun ($122,294), Fairfax ($110,674) and Arlington ($109,266) in Virginia, and Howard County ($107,490) in Maryland. The typical household in each of these suburbs makes more than twice the national median. Washington, in fact, dominates the top 30: A third of those counties are in this region.

The District of Columbia, at their center, doesn't compare with Philadelphia or Baltimore. The median income in the capital is $71,648 (well above the national median) — but that's still $50,000 less than in Loudoun.

There is, of course, plenty of wealth in D.C. as well. But Because Loudoun County has less poverty alongside it — wealthy suburbs are much more economically homogenous, often by design — the median income in the District is significantly lower.

Zoom out in the map above, and the highest-earning counties in America are notable not just for their suburban settings, but also their remarkable concentration on the east and west coasts. Where there is one super-rich county there, invariably there are several others nearby. Wealth doesn't just cluster at the neighborhood level or in particular suburbs. It carves out entire domains of the biggest metropolitan areas on the coasts.