The Truman Capote novel "In Cold Blood"
was based on the real-life murder of
what family in what town ?

Like the title says. IN COLD BLOOD dramatizes actual events and people in a realistic, technically well-crafted fashion, based upon Truman Capote's "nonficton" novel. Capote seized upon the real-life November 15, 1959 mass murder of the Clutter family in Holcomb, Kansas, by two psychopathic killers, and turned the grisly tale into a bestseller. In making the movie, director Brooks avoids further analysis, laying out the story of Smith and Hickock as faithful docudrama

Correct indeed !

Thanks for the answer Enthusiast Jenny !