Fifth richest: Arlington County, Va.
Median household income: $94,986
Living in Arlington isn't cheap, so you'd better be making at least the median household income to live in this county just outside Washington, D.C.
Arlington may not be the richest, but it does set a record for real estate values. The median value of owner-occupied homes in Arlington county is $571,700 -- almost $70,000 more than any other county on our list.
This county also stands out as the most educated on our list -- 70.1% of residents hold a bachelor's degree or higher.

Fourth richest: Hunterdon County, N.J.
Median household income: $97,874
The richest county in New Jersey, Hunterdon just missed the six-figure mark in median household income. Located just west of Somerset County, which took the eighth-richest county spot, Hunterdon's income has actually crossed the $100,000 mark before.
While some might assume Hunterdon's residents make high salaries by commuting to New York City, where salaries are higher than the national average, the truth is that almost 94% of residents stay in-state for work. In fact, more residents commute to Pennsylvania for work than New York.

Third richest: Howard County, Md.
Median household income: $101,771
With an astounding 58.3% of residents holding a bachelor's degree or higher, Howard County shows that higher education can pay. One of only three counties that have a six-figure median household income in the U.S., Howard is between Baltimore and Washington, D.C., attracting the extremely affluent. The median value of owner-occupied homes in the county is $456,200.

Second richest: Fairfax County, Va.
Median household income: $103,010
Fairfax County is one of the largest counties in terms of population to make our list (1,081,726 residents in 2010), but it is also notable for its real estate. Fairfax is one of only two counties on our list to break the half-million mark in home values. Coming in at $507,800 for the median value of owner-occupied homes, the county truly has some spectacular real estate.
Government buffs will be excited to learn Langley (headquarters of the CIA) is within the county line, so government employees must be making a decent amount of money these days. Also, the unemployment rate in the county has been astoundingly low historically, hitting 1.4% in 1999.

The richest county in America: Loudoun County, Va.
Median household income: $119,540
With a median household income that is a full $16,000 higher than our second-place finisher, Loudoun county has trounced the competition on its way to becoming the richest county in America.
Another county surrounding our nation's capital, Loudoun borders West Virginia and Maryland and is the home to Washington Dulles International Airport. The Appalachian Trail runs along its western border and the area was largely an agricultural community until the airport was built in the 1960s.
The population has continued to increase, with the area nearly doubling in population size from 2000 to 2010. The poverty rate is also at an incredibly low 3.2%.

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