"Another Word for Map is Faith", Christopher Rowe

SS F&SF (Fantasy & Science Fiction) AUG 2006
In a future very Christian America, a teacher/reverend and her students try to make the world as it was mapped. They are in the wilds of Kentucky. They want to correct a ridge and valley of its so-called sins.

Some interesting details, but I wasn't sure for most of the story where it was going.