Why is Pleasant Grove, Arkansas so murdery?

Pleasant Grove, as James and Jimmie tell it, is a dot in Stone County just outside Dover, population 335. It began as Red Stripe, after the red iron ore in the soil, sat first in Independence County and later in Stone, got a post office in 1912, and then shed the name altogether because a murder case had given it bad publicity. A town small enough to be renamed by a headline, in other words.

Its league position is not the work of many episodes adding up. All sixteen murders within 25 miles sit inside the town itself, all dated December 1987, and all sixteen come from a single episode, 501. No drift across decades, no help from neighbouring towns: one case, one episode, sixteen victims, rank 42 overall and first in Arkansas.

Worth saying plainly that this counts the show's cases, not crime in Arkansas. The show chooses which towns to visit, and here it visited once, thoroughly.