Why does Capote spend so much time describing Holcomb and it's geography?

Both the town and its geography help illustrate the crime and its aftermath. Dick and Perry choose this quiet isolated farm community for a few reasons. Neighbors are spread out and people. like the Clutters, keep their doors unlocked. There are plenty of directions to go once the crime has been committed. The rural landscape also defines the clutter family and the small town as well.