But, the county also reports that 7.4% of its 445,000 households, or almost 33,000, have an annual average income of less than $25,000, and that 18.4%, or almost 82,000, have incomes of less than $50,000.

In addition, more than 8% of Fairfax County's residents aged 25 and older had no high school education in 2013, the county reported, and roughly 36% of residents aged five and older spoke a language other than English at home during the same year.

"We had always had a Hispanic presence in the county and at the credit union, and while all Hispanic households were not low income, enough were that we began to sense a change in our membership," Thomas said.

In 2004, the cooperative applied to become a community chartered credit union and dropped the word "employees" from its name, Thomas explained.

Fairfax Country applied for and received recognition as a CDFI from the U.S. Treasury's Community Development Financial Institutions' Fund in 2009, and won its first CDFI grant to help address the needs of its growing Hispanic membership, Thomas said.

The $1.5 million grant allowed the credit union to fund a first mortgage program that defrayed some of the risk involved with making home loans to lower and moderate income borrowers, Thomas explained. The program, for example, enabled some borrowers to obtain loans with smaller down payments or at lower interest rates.

The cooperative also received an $8 million loan from the CDFI's Community Development Capital Initiative in 2010, and applied for recognition as a low-income credit union in the process.

"The two requirements for the CDCI money were that you had to be recognized as a CDFI and be a low-income credit union," Thomas recalled.

One of Fairfax County's two remaining trailer parks is visible from a balcony at the credit union.

The CDCI took funds that banks repaid as part of the Troubled Asset Restoration Program during the Great Recession, and loaned them to credit unions in low-interest, eight-year loans, which they could then use as secondary capital; the credit unions, however, were required to repay the funds in full.

As FCFCU worked through the CDFI recognition process with help from the National Federation of Community Development Credit Unions, analysts discovered that a full 70% of the credit union's member households qualified as low income, meaning they made less than 80% of the county's median household income.

"That blew me away," Thomas acknowledged. "I didn't realize it was that high."

FCFCU subsequently applied for a low-income designation. Thomas thought it would be an easy sell, but the NCUA rebuffed the cooperative at first, he said.

"I won't tell you who, but an NCUA official told me right away that there was no way he would recommend the agency recognize us as a low-income credit union," he said. "When I asked him why not, he told me, 'If I approved a low-income credit union in Fairfax County, the ABA would crucify me.' I asked him, 'Since when did the ABA set policy for us?'" Yet, the official still refused.

Undeterred, Thomas sent in the application along with redacted copies of member records that showed only their zip codes and incomes, to each NCUA board member. It was after this move that the agency agreed to recognize the credit union as low income.

Since then, the credit union has continued to offer the types of high-quality, low-cost financial products and services that all its members use, Thomas reported. Moreover, while it has missed the lion's share of the auto lending boom because it no longer does indirect lending, Thomas said the credit union continues to make progress with its personal loans, credit cards, mortgages and home equity loans.

During a tour arranged for CU Times of the cooperative's modernist-style headquarters, Thomas paused on a balcony and pointed out how the credit union's immediate neighborhood reflected its role as a CDFI in such a wealthy county.

Directly next door to the credit union and visible from its balcony stands the Waples Mobile Home Park – one of two mobile home parks in the county, Thomas noted. Just a few blocks behind the credit union are million dollar condominium developments, where several elected county officials reside, while across a major highway and to the south are construction sites for apartment complexes where, Thomas said he had been told, rents will be in the thousands of dollars.

"Just because a county can have pockets of wealth, that doesn't mean it doesn't also have broad areas of lower and middle income people who need the kinds of services a credit union can provide," Thomas said.