It takes a special kind of lawman to carry on for 20 years in the Wild West of TV. Matt Dillon, the mythical marshal of Dodge City, stood tall — all 6 feet, 6 inches of him — on "Gunsmoke" from 1955 to 1975. He outlasted dozens of other Western heroes while making history on TV's longest-running dramatic series, a record that held until NBC's "Law & Order" tied the CBS Western's record in 2010. Through all those gunslinging years, James Arness, who died Friday, kept Marshal Dillon righteous, peace-seeking and, most of all, believable.