Why is Iowa a blue state?

[Asian Nazi]

Settlement patterns.  Much of Eastern Iowa, like the rest of the Driftless Area, was settled by less wealthy farmers from New England and Scandinavia.  This is opposed to the much more arable Western Iowa, which was grabbed up by wealthier German and Dutch settlers.  If you look at an election map, you'll see that Eastern Iowa represents a political continuum with neighboring regions of MN, WI, and IL, while Western Iowa votes much more like Nebraska.  

Though as youngconservative points out, Iowa is hardly a solid blue state.  It leans that way a bit in presidential elections, but the state as a whole is rather elastic and swingy.  

[Asian Nazi]

The Midwest in general trending republican is one.

[citation needed]