Do the leaves have samara that is u-shaped or samara blades that are split very wide?
Samara is U-shaped
Leaf has 5 lobes with rounded sinuses; samara is U-shaped
OR
Samara is split wide
5 to 7 lobes with rounded sinuses; samara blades split apart very wide; leaf petiole is red; sap is milky -- [Norway Maple - not native to Iowa]