Which competitor to "Strange Stories" was edited by John W. Campbell?
Strange Stories:  "Strange Stories" was a competitor to the established leader in weird fiction, "Weird Tales". Strange Stories:  With the launch, also in 1939, of the well-received "Unknown", "Strange Stories" was unable to compete. Unknown (magazine): Unknown (also known as Unknown Worlds) was an American pulp fantasy fiction magazine, published from 1939 to 1943 by Street & Smith, and edited by John W. Campbell.
"Unknown"