The Rocketeer was created in 1982 by the late Dave Stevens as a tribute to Depression-era movie serials and comic strips and such. Stevens had an affinity for the pop culture of the first half of the 20th century, having made a career of creating art in the style of that bygone era. Besides The Rocketeer, his best-known works were his illustrations of pinup model Bettie Page (who was also a supporting character in The Rocketeer).
The Phantom was created in 1936 by the late Lee Falk (who continued to write and draw The Phantom comic strip until his death in 1999 at the age of 87), and was the very type of adventure story that Stevens was nostalgic for and trying to re-create with his Rocketeer character.
Both characters were adapted into live-action movies in the 1990s that took place in 1938 and would prove to be disappointments at the box office.