NW Iowa is a dead zone not because of traffic, but because it's NW Iowa. SW Iowa is also a dead zone. As is SE Iowa. It has nothing to do with roads. The middle of Nebraska is also a dead zone, and it's got interstate 80 running smack through the middle of it. Roads don't generate business, population generates business.
Not exactly true.
When a company considers locating in Iowa, a city can offer a lot of incentives to put jobs in their town. It's especially attractive if the average wage for the area is fairly low.
But if there isn't clear access to a four lane highway for logistics purposes, most companies won't even consider the location. The area is simply strangled economically.
Take Muscatine (my hometown), for example.
US 61 runs from Davenport to Muscatine, four lane through the entire county. Eventually, 61 hits St. Louis--not only another market, but a transportation hub.
However, when the push was on to make 61 four lane, Louisa County couldn't come up with the matching funds. So 61 is strangled at the county line (nearly to Burlington), and companies don't really consider shipping that route en masse.
I'll also add that Muscatine has a to negotiate some of the turns on county roads that are the more direct routes (though Moscow). Slowing laboriously through West Liberty is hardly preferable, either.
So while HNI, Bandag and the other industries in Muscatine might hope for better transportation links, they make do with what they've got, and are thankful for the Muscatine-Davenport link. And watch that side of town flourish.