With Thanks to Zoot Radio, the Audio Museum
"The Adventures of Philip Marlowe was a radio series featuring Philip Marlowe, the private eye created by Raymond Chandler. "The A to Z of Old Time Radio" by Robert C. Reinehr and Jon D. Swartz noted that the program varied in its genre from most others: "It was a more hard-boiled program than many of the other private detective shows of the time, containing few quips or quaint characters."
The show first aired on NBC radio on 17 June 1947 under the banner of The New Adventures Philip Marlowe's, with Van Heflin portraying Marlowe. Chandler's short story, Red Wind, was adapted for the first episode. The series on NBC concluded on September 9, 1947. In 1948 the series moved to CBS, where it was renamed The Adventures of Philip Marlowe, with Gerald Mohr playing Marlowe, For 114 episodes, the CBS version ran. The series took place from 26 September 1948 to 29 September 1950."