Foo Bar and Grill

Every so often, I hear someone pronounce "Oregon" "o-re-GON", with the stress on the last syllable, like "Polygon". This is always rather jarring, since I've never heard someone from the state pronounce it that way. My grandmother lives in Grants Pass and pronounces it "OR-eg-en", as does pretty much everyone else I've met in the state.

So, if any Oregonians are reading the site, what is the official pronounciation of "Oregon"?