It's a hard point to argue. Before there were formats, technically everythign was freeform in a way. Really before about 1935 it was hard to tell who was taking radio seriously and who was not. In 1947 It was abundantly clear that Jim Hawthorne was not. NOTE: not to be confused with james Hawthorne of the BBC or the other Jim Hawthorne the sportscaster.
Many operate under the assumption that free-form radio as we know it today began on 94.1 KPFA Berkey, CA. The first NCE licensed station in America and crown Jewel of the Pacifica Nework. But it was not so. Before they took to the air Jimbo was running amuk. On his show at 1110 KXLA-AM, he played a bizzarre array of Buddy Baker, Spike Jones, Red Ingle, Slim Coates, and all without regard to genre and format. That was way back in 1943!
His popularity was such that he managed to score a late night talk show on KLAC-TV it was kind of a predecessor to NBC's Saturday Night Live according to the Los Angeles Times. He maged tsome spots in some movies and even did some pre 3-stooges reels for film. Everything he did was counter to radio culture at the time.
His effect was barely noticed while he was active in broadcasting. It's only now that in looking back you can see the effects ripping outward. His zany all night weekend show on KOA radio was the stufff of legend. WFMU has a little tribute page here. and his fan club is here.
he's got a radio pedigree a mile long. This is far from complete...
KMYR Denver 1941 - 1943
KXLA Los Angeles, 1943 -1948
KECA Los Angeles, 1948 -1950
KNX Los Angeles, 1950-1952
KCBH Los Angeles, 1952 -1955
KYA San Francisco 1957 -1959
KDAY Los Angeles, 1959 -1960
KFWB Los Angeles, 1960 - 1963
KOA Denver, 1974-1981-1984
KIEV Los Angeles, 1991
Today Jim Hawthorne is 88 years old, living in a retirement home in Santa Barbara, California. He's grown comicly cantankerous bemoaning the state of modern radio, it's voice-tracking and control by megacorporations. He still does a local TV show in Santa Barbara four times a year