 WVON debuted on April 1, 1963 and quickly became a success playing R&B music, becoming the second most listened to Chicago station during evening hours by early 1964.97.9 WEHS's call sign was changed to WHFC, and simulcast WVON's programming until 1965, when 97.9 adopted a jazz format as WSDM.WVON ran 1,000 watts during the day and 250 watts at night.