Great question,combrade. It was Katherine Ross for me,in 1969 Butch Cassidy & the Sundance Kid.

In as early scene with Redford while her glossy mane is up, he tells her to ' let down your Hair~~~~~~shake your Head ' !!

Her silky Hair tumbled so wonderfully that you can HEAR it.

I knew I was hooked on Long Hair forever, and I was 10