In the 1930s, the riding pants type of thing, popular in the southwest in the 1920s, was disappearing- forget what they were called. I have pictures of my mother, one from the 20s shows her in the riding pants at an oil rig (no horse) and others of her in Levis from the 1930s and 1940s. I guess she didn't subscribe to Vogue magazine. She did wear skirts to town social events or shopping when we went to the big city (Denver or El Paso).
And as Nerd says, you are forgetting the lighter weight denims that are still popular.
And thanks for the picture of Rosie. I remembered the song but not the picture.