I live about a mile from the river so we've had our share of mosquitoes. My dad is a bird enthusiast so we put up bird houses for swallows. Swallows are great at keeping the bug population down. I don't know a lot about the bird population in Iowa so I don't know if that's a feasible option for you.
I do know that increasing your Vitamin B12 intake will keep the mosquitoes from biting. There is something in the B12 that causes a mild smell (undetectable by humans) that the mosquitoes don't like. I take a B50 complex
It will makes your urine a bright yellow (think fluorescent) so don't be alarmed the first time you go to the bathroom after you start taking it.
It should also be said that because this only keeps them from biting they do tend to buzz around you so it is probably best to implement some other form of repellent.