I think you are referring to the film of J. Robert Oppenheimer getting off the Chili Line coach.
Don't forget the reason Los Alamos was chosen as the home for the Manhattan Project Scientists. Oppenheimer was familiar with New Mexico because he'd been taken there as a teen to recover from colitis. He and his brother went there often through the 30s for hunting and horseback riding. They even owned a ranch in the area. Los Alamos was one of several sites they looked at, and was chosen because it was on a mesa, remote from outsiders, hard to get to, and protected from flooding.
The film was from Oppenheimer's home movies, and was taken in the area. Only thing is it was taken several years before the war, when Oppy was just a young professor at University of California.
Hope this helps.