Encore Western Channel airs "Gunsmoke" and "Marshall Dillon" quite a bit. It's one of the reasons I subscribed to U-Verse 300 for a year or two. I wanted the Westerns on the Encore Western Channel. Gunsmoke, Bonanza, The Big Valley, The Rifleman, Death Valley Days, Maverick, and of course, The Wild Wild West. They also showed some excellent Western movies like Ford's "Stagecoach".
When I was a Senior in College, "Maverick" was in reruns at noon on a local channel. It caught on for some reason with us. We'd all sit in the Quad and watch "Maverick" and then talk about it until we started talking about Stereos again.
Most of the old Westerns are available for viewing in their entirety on Youtube.
I grew up watching Gunsmoke and Bonanza. My Grandfather watched me a bit when my parents were away and I loved both of those shows.
I love the "Network Plug" for Gunsmoke by John Wayne that Trans posted. I've watched it a few times. Wayne is a very laid back salesman.
I love the plug for his young friend Jim Arness.
There is also one on Youtube where James Arness is plugging the show to Network in 1962-ish. I can't find it lately, but I know it's on there. It's a fairly long plug where he takes you behind the scenes a bit. Pretty interesting. Worth hunting for.