After my latest excursion to the northwest (more on that eventually), I have been to or through all by 15 of Iowa’s 500 largest cities.
The top of the “unvisited” list is Blue Grass (#211), by virtue of not really being on US 61 anymore, followed by Fruitland (#288), also by virtue of not being on US 61 by the letter of the law.
I haven’t updated my Clinched Highway Mapping page yet, but there are only four segments of state-maintained road I have not traveled since Jan. 1, 2003: Part of IA 9 in Howard County, four-lane US 63 south of IA 346, the Fort Madison bypass, and IA 1 north of Mount Vernon. New US 20 will be added shortly, in two bursts or possibly one. I think I’ll have to extend my time frame to 11 years instead of a decade for every mile of every road.