I'm from Iowa. There are a handful of population centers, and a sprinkling of homes and small communities between miles and miles and miles of farmland. The thing is, most people don't travel between the small communities - most driving takes people to or from town. If they're not going to town, they're going to visit neighbors or their fields, in which case gravel roads work great. Gravel roads work better than dete…
Iowa: 114,429 miles of roads
Wisconsin: 115,145 miles of roads
Source: http://www.fhwa.dot.gov/policyinformation/statistics/2013/hm10.cfm
Unpaved Functional Length:
Iowa: 13,363 miles
Wisconsin: 566 miles
Paved Functional Length:
Iowa: 81,273 miles
Wisconsin: 102,482 miles
Source: http://www.fhwa.dot.gov/policyinformation/statistics/2013/hm51.cfm
I think you need a better Department of Transportation, because even the population difference shouldn't really account for that huge of a gap. Population:
Iowa: 3.107 million
Wisconsin: 5.758 million
Source: https://www.wolframalpha.com/input/?i=iowa+wisconsin+population
Square miles:
Iowa: 56,270 sq mi
Wisconsin: 65,500 sq mi
Source: https://www.wolframalpha.com/input/?i=wisconsin+square+miles
Source: https://www.wolframalpha.com/input/?i=iowa+square+miles