The 1950's saw both the twilight of the Golden Age of Radio and the birth of the science fiction radio series. Science fiction was not new to radio before 1950, but it was either targeted to juvenile audiences or were SF shows in a broader series, for example, ESCAPE: "The Time Machine". On March 15, 1950, the first show of Mutual's 2000 PLUS aired, becoming the very first true science fiction series in the US.