WMERC-TV was signed-on by the National Broadcasting Company on September 30, 1958; it was one of the network's original owned-and-operated stations, along with WNBQ-TV (now WMAQ-TV) in Chicago, and WNBK-TV in Cleveland. It was also one of the first television stations in Indiana to sign on.
In mid-1978, as a result of NBC's ratings declining at the time, the network sold WMERC-TV to the Sinclair Broadcast Group, which has served as the station's owner since then. Because of its former ownership by NBC, channel 15 to this day is the only major television station in Mercury not to have changed its primary affiliation.
- WMERC-TV's mascot since 1992 has been an animated character known as Sailor Mercury. As Sailor Mercury has remained as the mascot for WMERC-TV, the station's logo since then has deleted the 1979-2004 NBC Peacock (to be replaced by NBC in 2005 with the Lucky Feather logo, which it still used until the return of the 1979 Peacock in 2019), and has incorporated her.
- At one point in mid-1995, Michael Eisner requested WMERC-TV to switch to the Disney Network, but Sinclair turned down the offer. As a result, the Disney Network affiliation went to then-Fox affiliate WUFUZ-TV.