James Arness, who burnished the legend of America’s epic West as Marshal Matt Dillon, the laconic peacemaker of Dodge City on “Gunsmoke,” one of the longest-running dramatic series in television history, died on Friday at his home in Los Angeles. He was 88. A family spokeswoman, Ginny Fazer, confirmed the death. Mr. Arness was terribly shy and had almost no training as an actor. A wartime leg wound made it painful for him to mount a horse. But he became the best-known tin star of his era, portraying the towering, weathered marshal for 20 years, from 1955 to 1975. He...