I wonder why.

Hollywood and High tech are in Southern California, so obviously their methodology is wrong.

Yeah, I was wondering about that. 

Gregory Alan Bolcer's comment reflects a number of false assumptions.  First that Hollywood is creative.  Second that tech "is in" Southern California, see http://venturebeat.com/2016/08/28/in-5-years-the-midwest-will-have-more-startups-than-silicon-valley/ or that tech in Southern California is particularly creative (a billion dollars for an app that adds filters to photos, for example, suggests that creativity is far from the priority; see also recent work on The Great Stagnation documenting how impotent technical "advances" have become in most cases).  Third that even if the premises held it would "obviously" reveal the methodology to be wrong.  The average IQ in New York is roughly 4 points lower than that of Vermont (huge gap) yet you will find dramatically more high IQ people in New York.  Saying one statistic makes the other "obviously wrong" means failing to understand basic statistics. 

Incidentally, a lot of the map can seemingly be explained by IQ differences but I'd guess not all.  The human brain can use 30% of energy at rest.  It may be that (more) people who enjoy using their brains a lot have a marginal preference for a cooler climate. 

"The creative class has, for better or worse, primarily been associated with big American cities along the coasts: out of Richard Florida's top 20 creative-class cities in 2015, only one — Dublin, Ohio — was located in a non-coastal state.

But new data recently released by the National Endowment for the Arts suggests that there's an awful lot of creativity happening far inland from America's coastal tech and arts hubs. 

Among other things, the NEA worked with the Census to poll residents of all 50 states on their participation in the arts, particularly whether they performed or created works of art in 2014.

Those data reveal a somewhat surprising pattern: America's Great Creative Divide isn't between the coasts and the center, but rather between North and South."

Cities makes more sense as correlation than north-south, to me. 

"Cities makes more sense as correlation than north-south, to me."

One of the basic points made by the researchers is that cities don't explain it.

Also I think urbanization is fairly homogenous, with the North and South each having one zone of hyper-urbanization (on the West and East coast, respectively).  Meanwhile, "The Southern U.S. experienced rapid industrialization after World War II, and is now over three-quarters urban, having almost the same urban percentage in 2010 as the Midwestern United States." (Wikipedia)

So creativity correlates with speed of industrialization?