It started with a boy and his dog. 19 years later, Lassie became more closely associated with the Forest Service, which would lead to an animated series.
Lassie aired on CBS from 1954-71, falling victim to the infamous "Rural Purge" that also claimed The Beverly Hillbillies, Hee-Haw, Mayberry RFD, and other shows set in rural or suburban areas, although an even longer running series, The Ed Sullivan Show, also left the air in 1971.
Like Hee-Haw, Lassie found new life in syndication, but only for 2 more seasons. My earliest memories of Lassie come from the syndicated era, as I barely remember any of the later CBS episodes, although some, I think, were mixed into the syndicated package.
Early episodes were syndicated under different titles. The first three seasons, with Tommy Rettig and Jan Clayton, were syndicated as Jeff's Collie, named for Rettig's character. Jon Provost succeeded Rettig in season 4, and the episodes from the Provost era were retitled, Timmy & Lassie. After producer Jack Wrather (The Lone Ranger) purchased the full rights to the series from Robert Maxwell (Adventures of Superman), Lassie found its way to color, and a change in format. Lassie became a mascot, of a sort, of the US Forest Service, and under the care of a series of Forest Rangers. After the final season, Filmation obtained a license from Wrather to create the short-lived Lassie's Rescue Rangers, which created a new supporting cast, including some additional animal Rangers. Filmation & Wrather would do business again on an animated Lone Ranger revival in 1980.
From 1968, here's the two-part "Track of the Jaguar", with Jed Allan (later of Celebrity Bowling & Days of Our Lives) as Ranger Scott Turner. Garry Walberg, later of The Odd Couple & Quincy, and Paul Petersen (ex-The Donna Reed Show) guest star.
I mentioned earlier that my memory is hazy on the show, so we'll forego a rating.