I understand there are a few areas like Dixville Notch, N.H where everyone in the area votes at midnight, and because they are so small they know everyone has voted and hence they can release their results are released at 12:01.
However, there are also some larger counties (with e.g. 10,000 people in them) that are announced at around 6pm, while polls only close at 7pm (e.g. in Kentucky, Indiana). How is this possible? I assume that they cannot know that everyone in the county has voted in the same why they know for Dixville Notch.