Thought the group might be interested in this analysis. Groups like NASS give weekly crop progress updates that show how corn is progressing at the state level. But there are not many options for seeing how corn is progressing within a given state. We have put together an analysis that estimates how far along corn is at numerous representative field locations in every major corn producing county in the Corn Belt. This analysis shows estimated intra-state variations in maturity, including details such as NW Iowa significantly lagging North Central Iowa, small areas of west central IL only at V6 while just a county or two over, crop is at V12 or V14, etc.
Full details of the analysis and state-specific maps can be found at http://insights.climate.com. We will be updating these graphics once a week for the rest of the season.