The Iowa DOT has incorporated the former iowadotmaps.com site (the URL still redirects) into the main iowadot.gov site, and that includes conforming to the (old) layout.
The pages with links to individual city, county, and traffic maps have been redesigned entirely. Most notably, the maps are now Flash-based (I think). When you hover over a county, or hover over a city after clicking on a county, that area now turns yellow. To view the county map, click on the county name at the top of each page. The cities are still reached by clicking on them. (These index maps were likely drawn in Illustrator, given their use of the Myriad font, and I’ve done that plenty myself.)
I’m not sure when this happened, but it had to be recently.