Hinkley Hills is the town where Mayfield Place is located.
Hinkley Hills is obviously fictional, but the opening scene zooms into the town from outer space, eventually pinpointing Mayfield Place, the main location of the film. Based on the zoom sequence, Hinkley Hills is located between the Missouri and Mississippi Rivers on about the same latitude as the southern tip of Lake Michigan, which places it in Iowa. The smaller rivers within the zoom sequence roughly resemble Iowa's river system, and the final location of the zoom places Hinkley Hills in Des Moines, Iowa.
Other than Mayfield Place, there are only a few known establishments. There used to be a soda fountain but it was torn down after Skip murdered his family and replaced with a shopping mall. Also there is a pizza restaurant that delivers and a delicatessen. Art mentions that Hinkley Hills used to be a lot safer because everyone knew everyone and nobody had to lock their doors at night.