Weather and prices drive it. I don't know the details of your area but if there's been a lot of wet weather well into spring the past few years (as there has been in parts of the South) then farmers will be shy about planting corn. For corn to be economical as an ethanol crop farmers need ethanol plants not only near by, but with good transportation to the plant.
(By the way, you may have read or heard that it takes more than a gallon of fuel to make a gallon of ethanol. Interestingly, that's true. What makes ethanol production feasible is the sale of the by-products of production, like animal feed. That makes it profitable on average about 7 out of 11 years, in Minnesota anyway.)
Overall, corn production in the US dropped about 8% last year over previous year. I'm not sure of how it was divided, but part of it was weather, and part of it was a big increase in the price of soy, which made soy a more lucrative crop.