Go with something native that has stood the test of time. If you go with the "new rplacement favorite" then 20 years from now you will have the same issue. Elms, Ash Honey Locust are all trees that landscapers fell in love with and over planted leading to huge monostands that are susceptible to disease/insects.
My personal favorite is the Gingko tree. Great yellow fall color, Unique leaf and texture. They are uncommon and pricey and you have to plant a male because the female's fruit smells awfull
Good info regarding native Iowa trees
http://www.iowanativetreesandshrubs.com/uploads/Nativetrees20.pdf