The station first signed on the air on June 5, 2007 as WHMM-DT. Channel 42 has operated as a digital-only station from its sign-on, as one of a handful of full-power television stations around the United States to sign on without a companion analog signal. The station debuted with an effective radiated power of 1 megawatt, the maximum wattage currently allowed by the Federal Communications Commission for digital television stations; as a result, KGLA-DT is the only full-power Spanish-language television station in the New Orleans market (Azteca America affiliate WTNO-LP (channel 22), which debuted in August 2006 as the first Spanish language station in the market, operates with a low-power license).
On April 23, 2007, Mayavision announced that it had signed an agreement with Telemundo to affiliate with WHMM-DT. Channel 42 was originally slated to debut in mid-May of that year, however its launch was delayed until the following month. At the time the station launched, the Hispanic population in New Orleans had increased between 2005 and 2007, from 6% to between 12% and 14%, which was attributed to the growth of re-construction jobs following Hurricane Katrina.
The station changed its call letters to KGLA-TV on August 27, 2007. On December 21 of that year, the "-TV" suffix in the station's callsign was replaced with a "-DT" suffix. KGLA's city of license, Hammond, and its transmitter in Metairie, are both located east of the Mississippi River, making it one of the few broadcast stations in the country whose callsign begins with a "K" that is licensed to a location east of the Mississippi River. The KGLA callsign was grandfathered to the television station, from Gretna-licensed radio station KGLA (1540 AM), which Mayavision owns a 50% ownership stake in conjunction with co-owner Crocodile Broadcasting. The station launched its own website in late 2007.