Arlington, Virginia

Although Arlington does not have the formal classification of independent city or incorporated town under Virginia state law, it is considered the second-largest "principal city" in the Washington metropolitan region.

Arlington, Virginia isn't often thought of as one of the most expensive areas to live in the United States. However, given its closeness to the nation's capital, Arlington's high cost of living begins to make sense. Arlington, which is located directly over the Potomac River from Washington, D.C., is legally a county, not a city. In reality, it is the smallest self-governing county in the United States.

Arlington also houses the Pentagon. As a result, a sizable section of the county's population is made up of well-paid government employees. As a result, Arlington's cost of living is 50.5 percent more than the national average. Rent and mortgages, for example, will cost residents 2.5 times more.

Cost of Living: 50.5% higher than U.S. average