In the 1965 film 'The Sound of Music', what is the name of the oldest child in the Von Trapp family?

Great movie. Julie Andrews voice and that opening scene will never be recreated ..

Although I have heard most of the songs from the film and seen clips( mainly at Xmas every year) I still haven’t watched from start to finish

I like to have a few and sing along. By Doe, a Deer, I’m usually asleep.