Fruit is an Acorn?

Do the leaves have 4 lobes or more than 4 lobes?

 4 lobes on leaf

Fruit is a cone-like group of samaras; leaf has 4 lobes; lead is 4 to 6 inches long; leaf tip is flat or notched [Yellow Poplar -- not native to Iowa]

OR

More than 4 lobes on leaf

 Fruit is an acorn; more than 4 lobes present