I can give anecdote from St Louis region, which has ~40-50% of Missouri's population. Gas prices here are around $1.60
I live in one of the large metros in Ohio, prices are all still $1.30-1.50/gallon here. Like most of the locations in the article, I would guess the sub-dollar prices are very isolated locations or special circumstances (no-tax native american reservations like I saw in other comments?)