Hi, fellow Iowans. I have a few questions about county highway naming in Iowa.

1) This page says Iowa's naming convention is "County Hwy xxx", but everywhere I look in Eastern Iowa, I see "CR-xxx". Which one is correct?

2) When should a county route number be the primary street name, and when should it just be an alternate name?

Details: Sorry for the vague reference, but somehow I got the impression that the primary street name should always defer to whatever the road signs say at "most" intersections, even if it means the route number becomes the alternate name. I believe this "rule" is partially implied by this page, under "Highways through cities/towns", which says route numbers should defer to city street names within city boundaries.

Here is a permalink example from rural Illinois: Although this is "SR-78" zigzagging north-to-south across the map, its primary street name is always the local road name instead of SR-78. I can understand why that was done, because even though the state route is clearly marked at each of its turns, when you look at Street View, the vast majority of the intersections just have the little green street name sign.

Using that same logic, then--despite the good job Iowa does marking its county routes--it seems like any Iowa county route with a street name should have that as the primary street name, and the county route number as an alternate. This because "most" intersections with a county route have nothing but the little green street name sign. But again, I don't see it marked that way in Eastern Iowa, hardly ever. Is there a reason?