Why Gunsmoke Was Canceled After 20 Years (& Didn't Receive A Finale)

screenrant.com:

Here's why classic Western series Gunsmoke was canceled after 20 years and didn't receive a finale episode. Before it became a TV show, Gunsmoke started life as a radio program. While John Wayne was once reported to have been in contention for the lead role of Marshal Matt Dillon, this was eventually debunked, as it was unheard of for a movie star to switch to a TV series during this era. Wayne did, however, record an introduction to Gunsmoke's first episode in support of his friend James Arness, who did take the Dillion role.

Gunsmoke debuted on CBS in 1955, and the series became both a critical and ratings hit. It was also considered grittier and more grounded than the average Western movie of that time. The series would end up running for over 630 episodes, and was once the longest-running scripted primetime series — which is a record The Simpsons eventually broke with season 29 episode «Forgive and Regret.»

Related: Gunsmoke: The Long Ride Finds Marshal Dillion Framed For Murder

Arness also appeared in every single episode of Gunsmoke, which also saw countless future movie stars pass through it, including Kurt Russell, Jodie Foster — who actually appeared three times — and Burt Reynolds. Gunsmoke did consistently well in ratings throughout its run, though its popularity dipped in 1967, which saw CBS planning to cancel it. There was a public backlash to this, however, so the network decided to continue producing it. After Gunsmoke's season 20 finale «The Sharecroppers» aired, the cast and crew all expected to be renewed for at least another series, but CBS instead opted to cancel the show and replace it with sitcom spinoff Rhoda.

CBS likely felt Gunsmoke was outdated and wanted to replace it with more contemporary