Hey everybody,
I had always been curious as to why ALL of the gasoline in my area (Chicagoland/Lake County, IN) contains ethanol, so I did a little research. I found a couple of sites that I thought were interesting, so I figured I'd share them.

First, a link to areas in which the EPA requires "reformulated" gas to reduce emissions and smog:
Where You Live | Reformulated Gas | US EPA

The reformulated gas has to have a higher oxygen content, which can be achieved via MTBE (~15%) or ethanol (~10%). MTBE can be a nasty chemical that gets into your groundwater, so many states have banned it:
http://tonto.eia.doe.gov/ftproot/service/mtbe.pdf

And that explains why I can only buy E10. Just thought this might be worth sharing for those curious about the gas in their markets.