The 89.3 FM facility signed on November 29, 1997. WMSJ's programming had originated in July 1993 on 91.9 FM in Harpswell; after 89.3 went on the air, the 91.9 frequency was sold to the Bible Broadcasting Network and became WYFP. Originally known as "Joy 89.3," the station rebranded to "Positive 89.3" in July 2005. W260AS in Lawrence signed on in February 2008.
By September 2010, the station's owner, The Positive Radio Network, shared several board members with Bethesda Christian Broadcasting, another operator of religious radio stations; the following year, WMSJ was transferred to Bethesda. In January 2015, Bethesda Christian Broadcasting reached a deal to sell WMSJ to the Educational Media Foundation; upon closing, the station will join its K-Love network.