Comparisons to the likes of Clark Gable and William Holden may be a bit premature, but would be well to keep in mind. Sissy Spacek matches him. Of course, she is rural South by birth and upbringing, but there is much more to her performance than authenticity. She molds an extremely believable picture of a strong, modern woman in an old-fashioned setting. Spacek's character is required to bring in a corn crop all by herself, and she really looks like she can do it, and bake bread, and take care of her children, and rescue herself from peril if she has to, and be there for her man when he needs her.
Some people find Spacek to be plain, or even ugly.
I've always thought that she radiates an inner beauty based on strength of character. Her role in The River confirms my impression. As Rydell is also fond of saying, movies don't make themselves and they aren't accidents. His concern shows in The River . Rydell has also handled his actual direction duties very well.