J.C. Leyendecker was likely the most successful commercial illustrator in the first decades of the 20th century (before that honor belonged to Norman Rockwell). Famous for his illustrations of the 'Arrow Collar Man' and for his Saturday Evening Post covers (He painted something like 300 covers for them). His most famous image today is from a 1922 Life Magazine (not that Life, the other one) cover, called The Flapper. But, flappers aside, Leyendecker likely more responsible for how we picture men in the early 20th century than anybody else. He used as his model his "live-in companion", Charles Beach, with whom he resided for many decades. Leyendecker never officially came out, so this is all really speculation but, I mean, really. It's just unfortunate he lived in a time when such subterfuge was deemed necessary.
Sadly, the decline of the collar industry hurt his career and his close identification with the decadence of the 20s didn't help either, after the crash in '29. He spent the remaining decades of his life in his estate in New Rochelle, living in near seclusion with Beach.
Some examples of his lovely and elegant work are below: