KDNA selected FM radio when it was still newer technology, was not desired commercially, and thus it relatively cheap to obtain the widely open band space. As commercial radio developed the frequency became near the middle of the commercial dial and thus very lucrative. WBAI in New York City is one of the few remaining community radio stations in the commercial spectrum in the US, although community radio were early adopters of FM. Most community stations are now located in the lower end of the dial in the nonprofit spectrum. A successor of sorts to KDNA in St. Louis is KDHX.
