What is the importance of the setting (holcomb) in "in cold blood"

The importance of Holcomb is to establish that this crime takes place in "the heartland" of America. By establishing such a brutal crime in such a formerly peaceful and innocent setting, the author demonstrates that there is no place in America that is truly safe. This crime took place where people never even locked their doors, now the townspeople do not even trust each other. This moved the fear of crime from some distant, big city to small town America.