The Ragbrai map has certain road labels as indicated. What source are you comparing the route with?
Agree with UC, the initial route as published is tweaked when the final maps come out. A group called Geobike used to provide mapping info in conjunction with Ragbrai. They would publish GPS files shortly after the initial route came out. When the final maps appeared in early July, I would go back into my map editing software and verify the initial route with the final route. Often there were a few minor changes. To a majority of riders, this went unnoticed.
This year as well I put the route into the mapping software and will update as soon as the final version hits the newsstand.