Mississippi is like Bosnia

And Arkansas is like Russia

And Cuba is better off than both of them. Human development index is a more expansive measure than pure economic activity (like GDP). You're also looking at education and literacy, basic health. Iceland and other Scandinavian countries typically top the list. But when you break states off independently, we can see there's a core, mostly of the NE but also some other big states spread throughout the country, that fare just about as well as any nation in the world. The problem is that there's this core of Southern states that fare just about as badly as developing nations that drags the total national average down. Basically if you live in Kentucky, Tennessee, Arkansas, Oklahoma, Alabama, Louisiana, West Virginia, or Mississippi, you're living in a third world country. Presumably we could isolate further down and look at individual counties within these states and find that some of the cities might be doing fairly well within them, but others not so much.

What would be the cause of this disparity? Well educational systems in New England and portions of the Midwest are far superior when one breaks out individual state scores on international educational rankings. And the vast majority of the least healthy states are in that list as well. Now within the comments people are quibbling because there's Wal-Marts all over the place to make goods and services cheap and affordable. Likewise, the vast expense of buying arable or inhabitable land in California or NYC may inflate the GDP figures there. There may be a reason to adjust for cost of living within a nominal GDP calculation. But it would seem obvious that general lack of economic activity given within a cheap retail environment and a basically rural area with an undereducated and unhealthy population isn't a recipe for future growth either.

One other interesting part is the political disparity that this creates: the lower states also tended to go vote for "conservatives". In reference to the general anti-intellectual basis that "conservatives" have come to represent, this isn't terribly surprising that the least educated or developed states would somehow come to demand less progressive policies.

More interesting still is this map. Take a look at the Eastern economic development zones versus the rest of the country... You can clearly see Beijing, Shanghai, Guangzhou/Hong Kong. And then there's Tibet.