WFIU began broadcasting on September 30, 1950, building upon efforts by IU to produce radio programming since 1937. Originally broadcasting on 90.9 FM, WFIU moved to 103.7 FM in 1951. 103.7 had been WSUA-FM, a commercial station, between 1948 and 1950. The owners of WSUA donated the 103.7 transmitter to Indiana University after their station went out of business.
This move was required to prevent interference with the audio channel of WFBM-TV (now WRTV) Channel 6 in nearby Indianapolis, which was the CBS affiliate for central Indiana at the time. The poor-quality tuners of early TVs weren't selective enough to prevent the strong 90.9 signal emanating from the IU campus in central Bloomington from overriding the much-weaker Channel 6, which transmitted from about 50 miles away.
This makes WFIU one of the very few public stations in the U.S. to transmit on a frequency other than those between 88.1 and 91.9 MHz, the FCC's reserved part of the FM band for non-commercial use.
WFIU transmitted with an Effective Radiated Power (ERP) of 75,000 watts from the center of the IU campus until 1971. It moved to the tower of sister-station WTIU Channel 30 on the south side of Bloomington that year. The move not only increased its range, even with a lower ERP, but it cured another problem. Inexpensive FM radios in central Bloomington picked up the station all over the FM dial when it transmitted from campus. The move to the Channel 30 tower fixed that.
WFIU claims to have adopted in 1970 an almost entirely all-classical music format, featuring national programs as well as locally produced content. However, some long-time WFIU staff[who?] have stated that it was never a strictly classical station until the mid-1970s or later. It was one of the first 90 NPR affiliates to broadcast "All Things Considered" upon its debut in 1971.