All the states that we have crossed so far have sections that are uninhabited. Mountains, forests, deserts and other natural obstacles stand in the way of human conquest. Not so in Iowa. Incredible 99% of land is put to a productive use. With the exception of a few cities this means agriculture. Specifically, fields of corn. In a 100 years of settlement Iowa was so successful in cultivating prairie that at the turn of the 20th century there was none left for the federal government to put its paws on and convert into a national park as it was tempted to do in other states.
Extinct animals, discontinued cars and disarmed rockets meet their end at the Great Plains. Grass covers many a secret and is a great backdrop for modern art installations. You get extra points for confounding future archeologist: just to think that we may know as little about Stonehenge as they will deduce about Carhenge. In the 19th century prairie provided in abundance: land was parceled out to whoever would claim it, bones were dug up and carted off to whichever museum sponsored the dig. Military installations served the immediate purpose of suppressing native population.
This was always a land to be crossed as quickly as possible. Both for 19th century pioneers and for 21th century road trippers. The reasons might be different. Pioneers going West to Oregon and California thought of the prairie as a desert. No timber, no water, no soil good for farming. Little did they know that the land sits on top of the Ogallala Aquifer. Which happens to be the largest in the word.