Charles Edward Chambers (1883-1941) was a highly skilled and successful illustrator, though not as famous as some others active 1915-1940 who had more distinctive styles. His Wikipedia entry is here and Society of Illustrators 2010 Hall of Fame induction statement is here.
The Chesterfield billboard illustration above shows Chambers doing some of his best work for an important client. More examples of his illustrations are below. Given the length of his career, I wish that more of the Internet image sources had dates for them. They didn't, so I do a lot of guesswork in the captions.