The station serves the Upper Peninsula and northeastern Wisconsin. It first signed on in 1963 as WNMR. It joined the then year-old NPR in 1971 and adopted its current calls in 1975.
WNMU-FM is licensed to broadcast in HD Radio, but opted to temporarily discontinue HD broadcasting in the spring of 2011 due to financial constraints. The station had planned to launch HD-2 and HD-3 side channels, one featuring entirely classical music and the other featuring entirely public radio news and information. It had been the only Upper Peninsula radio station licensed for HD transmissions.
NOTE: W243CQ previously operated as W296AX on 107.1 FM. The translator changed frequencies due to the sign-on of 107.3 WUPF in Powers, Michigan, which serves the Escanaba area. Similarly, the Stephenson translator, which originally operated at 107.3, was forced off the air in July 2009 by the sign-on on WUPF. The translator received construction permits to move to 96.7 and 97.3, but transmission on those frequencies would have presented interference to WUPG 96.7 FM in Republic, Michigan, and WGLQ 97.1 FM in Escanaba, respectively. In June 2011, the translator was granted a construction permit to operate on 97.9, where it would not interfere in the protected coverage areas of any full-powered stations. That translator is now on the air at 97.9. Also, WNMU previously operated a translator in Menominee, Michigan at 91.3 FM (W217AA). As of May 2012, the license for this translator has been cancelled, due to the sign-on of WRMW, a full-power station on the same frequency in nearby Peshtigo, Wisconsin. It is not known whether NMU will seek another frequency in the Menominee area.