There were several illustrators whose careers were devoted to that subject, perhaps most notably Harrison Fisher, whose works dominated the covers of Cosmopolitan Magazine for the first three decades of the 20th century.
The present post deals with Bradshaw Crandell (1896-1966), who followed Fisher's footsteps to some degree, including creating cover art for Cosmopolitan. Crandell's Wikipedia entry is here. But artists might find this post on Leif Peng's blog of more interest. The writer, Kent Steine, describes Crandell's pastel layering technique used for much of his work up until the 1940s when he transitioned to oil paints. Pastel was popular for rendering women's faces because it could create a smooth appearance more easily than oil paints and without the fuss and potential for the artificiality of airbrush.
Crandell could and did create full-length illustrations of women and even could paint a man. But his fame was centered on depictions of women, some of which are shown below.
In the photo foreground are what appear to be boxes of pastel sticks.
This actually includes a man.
Again, just to show that Crandell could do more than women's faces.