100.9 FM began broadcasting in 1976 as adult contemporary station WRQN. In 1978, it was sold to the owners of 1310-WLOB-AM, at which time it was changed to album-oriented rock as WLOB-FM. During those years, it was known as "FM101-Portland's Best Rock", giving rock station WBLM some very serious competition and sometimes beating them in the ratings as well.
In late 1980, the station was sold to Eastman Broadcasting, which was also in the process of purchasing 970-WCSH AM, Portland, Maine. Eastman changed the call letters to WYNZ-FM in December 1980, but initially left the AOR format untouched. For the next year, the station was known as "Z101-Portland's Best Rock".
Some of the DJs on "FM101/Z101-Portland's Best Rock" included Danny Shewster, GV Rapp, John Clark, Karen (Tucker) Payson, Bennie Green, Scott Schuster, Will Jackson, and Jeff Spicer. Eastman changed WYNZ-FM to adult contemporary in November, 1981. That format remained in place until the late 1980s, when WYNZ changed formats to oldies, as "Oldies 100.9 WYNZ."
In 2007, WYNZ evolved to a classic hits format, as "Big Hits Y100.9." In 2009, the station changed its city of license from Westbrook to South Portland.
In April 2013, WYNZ has rebranded as "Rewind 100.9", returning the oldies format to WYNZ since it became a classic hits station in 2007.