The Richest County In The United States
When a county is described as the richest in the United States, median household income is one of the most commonly used measures. It represents the midpoint of household incomes in an area and differs from per capita income, which divides total personal income across the population, including children. Neither measure represents accumulated wealth, home equity, or net worth. According to the latest 2020-2024 American Community Survey five-year estimates, Loudoun County, Virginia, ranks first among US counties and county equivalents in median household income, at $181,765.
Loudoun also has a high per capita income, at $71,986 in the same 2020-2024 dataset. Its position differs under that measure because household income is affected by factors such as household size and the number of earners within a home. For a nationwide comparison of counties, median household income provides a consistent measure of what the typical household earns.
How Loudon County Stacks Up
The Census Bureau publishes American Community Survey estimates in one-year and five-year forms. One-year estimates provide a shorter-term snapshot, although they are limited to areas with populations of at least 65,000. Five-year estimates combine 60 months of survey responses and cover counties and county equivalents regardless of population size. That broader coverage makes the five-year dataset the more suitable choice for a nationwide county ranking. The latest five-year release covers 2020 through 2024 and reports incomes in 2024 inflation-adjusted dollars. It puts Loudoun County's median household income at $181,765. The national median for the same period was $80,734, while Virginia's was $93,170. Loudoun's figure was therefore more than twice the national median and close to twice the statewide figure.
The Bigger Picture
Loudoun County sits in Northern Virginia within the Washington, D.C. metropolitan area. Its economy includes federal government contracting and information technology. Aerospace and defense are also major sectors. The county is especially well known for its enormous data center industry, concentrated in an area commonly known as Data Center Alley.
Loudoun is one of several high-income jurisdictions around Washington. Five Virginia or Maryland counties and county equivalents appear among the top 15 in the 2020-2024 ACS five-year ranking. Fairfax County ranks fourth with a median household income of $153,637, while Howard County, Maryland, ranks fifth at $149,763. Falls Church, an independent city in Virginia treated as a county equivalent by the Census Bureau, ranks 11th at $143,262. Arlington County ranks 12th at $142,114.
The concentration of high incomes around Washington reflects the region's large professional workforce and extensive federal contracting sector. Technology is also a major employer across Northern Virginia. Loudoun ranks above its regional peers in the current ranking, with a median household income more than $28,000 higher than that of neighboring Fairfax County.
Other Top-Tier Counties
California has several counties near the top of the national ranking. Santa Clara County, home to much of Silicon Valley, ranks second with a median household income of $164,281. San Mateo County ranks third at $158,855. Marin County is seventh at $149,091, while San Francisco County ranks 14th at $140,970. Outside California and the Washington region, Douglas County, Colorado, ranks sixth at $149,594. Los Alamos County, New Mexico, is eighth at $147,139. Nassau County, New York, ranks ninth at $146,202. Forsyth County, Georgia, completes the current top ten at $143,784.
Los Alamos shows how different local economies can produce exceptionally high household incomes. The county is home to Los Alamos National Laboratory, by far its largest employer. Its concentration of scientific and technical employment helps explain why a county with fewer than 20,000 residents can rank alongside wealthy suburban counties surrounding some of the country's largest metropolitan areas.
How Rare Six-Figure County Incomes Actually Are
Six-figure median household incomes remain uncommon at the county level. Among roughly 3,143 counties and county equivalents in the 50 states and Washington, D.C., 168 have median household incomes above $100,000 in the 2020-2024 ACS five-year estimates. That works out to about 5.3% of the total. Many of these high-income counties sit within or near major metropolitan areas, including Washington, San Francisco, New York, and Boston. Wealthy suburban counties also appear around Denver and other growing employment centers. Their high median incomes frequently coincide with concentrations of professional, technical, financial, or government employment.
Rural counties can follow a very different economic profile. Median household income measures income received by households. It does not measure land values, mineral reserves, agricultural production, or total economic output. A county can therefore generate significant farming or energy activity while recording a considerably lower median household income.
The Bottom Line
The 2020-2024 ACS five-year estimates place Loudoun County at the top of the national county ranking with a median household income of $181,765. Santa Clara County follows at $164,281, leaving a gap of $17,484 between the two published estimates. ACS figures are survey estimates with margins of error, so rankings can change as new data are released. The current five-year dataset, however, clearly places Loudoun first among US counties and county equivalents by median household income.
