(CNN) — CNNMoney looks at the five states with the biggest differences in middle class incomes.
Virginia is the most unequal when it comes to comparing median income by county.
Loudoun, a wealthy county near Washington D.C., has four times the median income of Buchanan, a struggling county in the southwestern portion of the state.
Home to Washington Dulles International Airport, Loudoun is one of the fastest growing counties in Virginia. Its population has surged 12% to nearly 350,000 between 2010 and 2013, compared to a 3% growth rate for the rest of the state.
A desirable DC suburb, Loudoun has attracted a lot of wealthy, young families, said Hamilton Lombard, demographic researcher at the University of Virginia. The eastern part of the county is well-developed, while wealthy horse farms dot the western portion.
Many Loudoun residents are employed by government contractors, particularly defense firms. Tech companies are also numerous. Its unemployment rate is only 4.4%, and its poverty rate only 4%, compared to 5.4% and 11.8%, respectively, for the state.
Buchanan, on the other hand, was the state’s bright shinning star a century ago when coal was king. The population of the county, which borders Kentucky and West Virginia, grew 1,500% between 1870 and World War II, Lombard said. The coal industry, as well as supporting businesses, drove much of the state’s economy in the early part of the 20th century.
But mining coal underground, as is done in the area, has fallen out of favor. Residents fled, leaving only about 24,000.
Unemployment stands at 9.9%, while 23% of residents are in poverty.
Oldham County, which has the highest median income in Kentucky, lies near Louisville, the state’s largest city. A mix of farmland, small towns and bedroom suburbs, Oldham sits on the Ohio River and is on an interstate highway, making it easy for residents and companies to get around.
Many Oldham residents work in white-collar jobs in finance, insurance and real estate firms in Louisville. Some 92% have at least a high school degree and 39% have at least a bachelor’s, higher than the state average. Unemployment stands at 6.3%, lower than the state’s 7.4% rate, while only 6.7% are in poverty, far lower than the 19.3% state rate.
Clay, meanwhile, lies deep in the mountains in southeastern Kentucky. It’s among the poorest counties in the nation, with a poverty rate of 42%, said James Ziliak, director of the University of Kentucky’s Center for Poverty Research.
Its economic foundation was coal, which peaked in the mid-1900s. Now, jobs are hard to come by. The unemployment rate is 12%.
The New York Times recently declared Clay the hardest place in America to live, citing its high unemployment and poverty rates, low education levels and high obesity rates.
Starr County is “as close to a developing county as you can get and still be in the U.S.”
People live in clusters of trailers and homes with no electricity or plumbing, said Cynthia Osbourne, director of the Child and Family Research Partnership at the University of Texas-Austin. Dirt roads abound in this county, which borders Mexico.
Starr has none of the oil and gas resources that fuel the Texas economy. It’s mainly rural, depending on agriculture. And it has the lowest median income in the state.
Some 43.6% of residents live in poverty and unemployment is at 14.2%, far higher than the state’s 17.9% poverty rate and 5.1% unemployment rate. Fewer than half have high school degrees.
Some 96% of its residents are Latino, many of whom come from families who have lived in Texas for years. Only 31% are foreign born.
A world away is Rockwall County, which serves as a suburb of the Dallas-Fort Worth metro area. Residents are employed in well-paying jobs, including high-tech and engineering, said Steve Murdock, sociology professor at Rice University. Unemployment is a low 4.9%, and only 6.7% of the population are below the poverty line.
Between 2010 and 2012, the county had the second-fastest job growth in the nation — 13%, CNNMoney found. Among the industries expanding or relocating there were aerospace, logistics, defense and manufacturing firms.
One of the fastest-growing counties in Tennessee, Williamson serves as both a bedroom community for Nashville and a center of economic activity. That helps it secure the highest median income in the state.
A mix of rural areas, historic towns and suburban communities, Williamson is also home to the headquarters of Nissan North America, as well as Tractor Supply Company and Mars Petcare. Entrepreneurs make up 20% of the workforce, boasts the county’s Office of Economic Development.
Unemployment is only 5.4%, compared to 7.1% statewide. Some 6.6% of residents are in poverty, while 18% are statewide.
At the other end of the spectrum is Hardeman, which is in a remote southwest corner of the state on the border of Mississippi. A rural area, it doesn’t have easy access to markets, said Bill Fox, director of the Center for Business and Economic Research at the University of Tennessee.
Known as the hardwood capital of the state, Hardeman depends on a mixture of light manufacturing, wood milling and agriculture, according to the county Chamber of Commerce. It’s also popular with hunters and nature lovers.
That hasn’t translated into many economic opportunities for residents. The county’s unemployment rate is 10.2% and its poverty rate is 27.3%.
Forsyth County is home to well-off residents who work both in Atlanta and within its own borders. It has the highest median income in the state, three times greater than Grady County, which has the lowest.
A high-capacity highway takes people into downtown Atlanta, but Forsyth is also home to a Scientific Games International manufacturing facility and Siemens Energy & Automation.
Professional services firms, including accountants, consultants and engineers, are popping up, as are medical records and transaction processing businesses, said Jeff Humphries, director of the Selig Center for Economic Growth at the University of Georgia.
The unemployment rate is 5.9%, compared to 7.8% for the state. Only 6.6% are in poverty, while the state rate is 19.2%.
“It’s where executives want to live and it’s where the workforce they hope to tap into resides,” Humphries said.
Grady, on the other hand, is a small, rural county on the Florida border. Unemployment is at 7.3%, below the state average. The county has a diverse industrial base, with companies involved in boat building, food distribution, automotive parts and furniture making. Residents also work in Tallahassee, about 40 miles away.
The county also has agricultural businesses, growing cotton and peanuts, which employs many lower-paid workers. About one-third of residents are senior citizens, many of whom are on fixed incomes.
The poverty rate is 25.9%.