Where was this filmed

I grew up in the original setting of this story, which is from the eponymous novel by A.B. Guthrie, along the Rocky Mountain Front and along tributaries of the Missouri River in north central Montana. I recognize Guthrie’s descriptions of the landscape and landmarks (Ear Mountain, Missouri River and “Tansy” Teton River, etc.), which he also refers to or renames in some of his other novels: “The Big Sky,” “Fair Land, Fair Land” and “Arfive,” all of which go back and forth along the Rocky Mountain Front, among other adjoining western landscapes. It’s where Guthrie (1901-1991) also grew up and then returned to after his newspaper career in Kentucky and continued to write novels.

When I watched this 20th Century Fox movie, made around the time I was born, I tried to figure out where it was filmed. Though the landscape was beautiful and filmed well, it definitely was not made along the Rocky Mountain Front or anywhere else in the story’s birth place of Montana. The film credits don’t indicate an area and I haven’t found anything here in IMDb.

Considering all the Ponderosa pines in the movie, I’d estimate that at least some of it could have been filmed in Colorado or New Mexico, even, especially with some of the monoliths and mesas in the backgrounds. We have some hoodoos and sawtooth mountains in Montana, but not like the Monument Valley profiles in the earlier scenes of “These Thousand Hills.” Some of the other scenes look like "Bonanza" from t.v....so maybe it was all in the Tahoe area of California/Nevada....

Anybody have any ideas or evidence on where they filmed this movie?