From this Bloomberg piece, the surprising (?) answer to the place where the wealth gap is the highest in the United States:

Nowhere is the contrast between rich and poor clearer than in the metropolitan region abutting New York, stretching from Greenwich on the west to Bridgeport on the east. This 625- square-mile swath, where subsidized housing complexes sit blocks from multimillion-dollar mansions, is home to the widest income gap of any metro area in the U.S., according to Census Bureau data compiled by Bloomberg. If this region were a country, it would be the 14th-most unequal spot on the planet, ranking just below Brazil, based on figures in the CIA World Factbook.

The region is described as the microcosm of the United States:

Connecticut’s per capita income is the highest of any state in the nation at $36,775, according to the census. In the Bridgeport-Stamford-Norwalk metro area, 53,076 households took home at least $200,000 — and 16,505 earned less than $10,000.

And the startling statistic about Greenwich, perhaps the world capital of hedge funds:

One doesn’t need to leave the town to see disparity. About 2,150 of its 60,000 residents live in poverty, defined as less than $22,113 for a family of four, according to the 2010 American Community Survey. More than 10 percent of public school students are eligible for free or reduced-price lunch, the United Way’s Greenwich chapter says, and there are 1,195 units of subsidized housing.

On a related note: how is income inequality measured? It is via the Gini coefficient, defined per Wikipedia:

The Gini coefficient is a measure of the inequality of a distribution, a value of 0 expressing perfect equality where everyone has equal shares of income and a value of 1 expresses maximal inequality where only one person has all the income. It is commonly used as a measure of inequality of income or wealth. Worldwide, Gini coefficients for income range from approximately 0.23 (Sweden) to 0.70 (Namibia) although not every country has been assessed.

The United States’ Gini coefficient increased from 0.46 in 2000 to 0.469 in 2010. By comparison, the Gini coefficient for Bridgeport, CT was 0.537 in 2010, up from 0.459 in 2000.