Here is a map showing a regional breakdown of fast-food restaurants per capita. A more complex analysis can be found at Datafiniti.
“Southern states have the highest fast food count per capita. The top spot goes to Alabama at 6.3 restaurants per 10K residents. The only non-southern states in the top ten are Nebraska at 5.4 and Indiana at 5.0, both in the Central region. As for the states with the fewest fast-food restaurants per capita, most are from the Eastern region with Vermont having the fewest fast-food restaurants per capita at 1.9 per 10K residents. Mississippi made a surprise appearance with just 2.1 fast food restaurants per 10K residents.”