Why is unemployment in Yuma so high?

Yuma, Arizona, has the highest unemployment rate in the nation—27.3% in December 2012.

Here was a response at The Straight Dope website where readers write and respond that made the most sense, from a resident of Yuma :

Aside from agribiz, the two main employers are the Army (Yuma Proving Grounds) and the Marine Corps (MCAS Yuma). A lot of the testing and such is done by contractors in the defense industry. 

From my observation, part of the reason for the shortage of jobs is that the companies who subcontract at these bases tend to transfer in specialists from other locales, because few locals are likely to have the required skills or training needed. What's left over for the natives are jobs in the service sector--and employers hire as few people as they can operate with and then overwork them.

Another important employer (though this is changing, I hear) is the criminal justice system--the county sheriff, US Border Patrol, Customs, a big state prison, etc. A lot of those people are trained at the local community college, AWC. Criminal Justice is also a big major at the Yuma branch of Northern Arizona University.

There isn't a lot of industry because there isn't much room for it. Once you subtract all of the federal land (YPG, MCAS, the Barry Goldwater Air Force Range, and a couple of large wildlife refuges) and what's left of the irrigated farmland (what hasn't been developed yet), there isn't really much private land left over. There is a carpet fiber plant in the city (which seems to change name and ownership every couple of years), but it's mostly automated.

The Bismarck, North Dakota metropolitan area had the nation’s lowest unemployment rate of 2.2 percent.