James Arness just died (his brother, also a TV star, was the late Peter Graves). He played the title role in the original The Thing and made other films, but his most important role was as Matt Dillon in the TV version of Gunsmoke, taking over for the radio version’s William Conrad, who was physically unsuitable to play the part on TV. Arness became the ultimate TV Western hero, and the show became one of the longest-running weekly series in TV history. (The Simpsons has done more seasons, but not yet as many episodes.)
It was a very fine show, too, particularly in the early half-hour episodes adapted from the radio version, but it managed to produce some good episodes in all its incarnations, including the episode that so impressed John Gregory Dunne. As John Wayne said in his filmed introduction to the television version, it was an “adult, realistic” alternative to the usual TV Western. It wasn’t that realistic, of course, but the perception was that most television Westerns were aimed at kids. The producers of Gunsmoke deliberately went against that perception; that’s why the episode chosen for the premiere was an episode where Matt Dillon gets shot, showing instantly that this is not a kiddie show where nothing bad can ever happen to the good guy.
Here’s a link to Arness’s archive of American Television interview, and here’s an excerpt where he talks about the early days of the Gunsmoke TV series: