WNBM signed on as WFAS-FM in 1947, licensed to White Plains, New York targeting the Westchester County, New York suburbs. The station was initially full-service, before shifting to an easy listening format. This would evolve into an adult contemporary format by the mid-1980s.

Addition of HD radio

Cumulus Broadcasting began adding HD Radio broadcasting to its station in 2005. One of the first ten stations to add HD was WFAS-FM.

Format change

In order to increase their reach of the New York market, as well as increasing the value of the station, in 2012 Cumulus applied to the FCC for a construction permit to move the station's tower location to the Montefiore Medical Center in the Bronx and change the station's city of license to Bronxville to better target New York City itself. The permit was approved in mid-2013. Rumors on radio industry insider websites speculated that the station would flip to either urban contemporary (to compete against Emmis Communications' WQHT and WBLS and Clear Channel's WWPR) or modern rock (which would fill the format hole in the market after WRXP flipped to a simulcast of WFAN in November 2012). During the week of June 30, 2014, the station's on-air staff bid farewell. WFAS-FM signed off their White Plains transmitter on July 4 at Midnight, after a set of "goodbye"-themed songs, which ended with "Graduation (Friends Forever)" by Vitamin C (WFAS-FM would move their programming to the HD2 sub-channel of sister WPLJ, which replaced the True Oldies Channel after Cumulus announced the end of that network, which came a few days earlier). Later that day, at 9 AM, the new Bronx transmitter signed on, and 103.9 FM began stunting with a ticking clock. At 1:03 PM, Cumulus officially changed the format to Urban AC, branded as "Radio 103.9", under new call letters WNBM.