The 910 AM frequency signed on the air in 1939 as KVAN, airing a country music format in the 1950s. After being sold to the Star Stations group in 1959, KVAN relaunched as Top 40 station KISN, which was at times Portland's most listened-to station in the 1960s. A scandal involving political bias and a litany of indiscretions resulted in the FCC revoking the licenses of all five Star Stations, including KISN, in 1975; the stations left the air September 2, 1976.
New licenses
After the FCC revoked the KISN license, four applications were received for the vacated frequency, from Rose Broadcasting, Viking Vancouver, Fort Vancouver Broadcasting and Longwood Broadcasting; the agency designated these applications for comparative hearing on July 12, 1978. The applicants merged in 1979 under the Fort Vancouver Broadcasting application, enabling the FCC to issue a construction permit. The new station took the call letters KKSN—the KISN calls having been assigned to 97.1 FM in Salt Lake City, Utah, on May 8, 1978—and began broadcasting April 1, 1980, trading on the "Mighty 91" name and KISN heritage. Former KISN sales manager Bill Failing served as the first general manager of the new KKSN. In its history since returning in 1980, this frequency has aired numerous formats, including classical, oldies and adult standards. On March 30, 1998, as part of a format swap, the "Sunny" format would move to 1520 AM, while 910 became home of sports radio station KFXX, which would move to 1080 kHz on March 18, 2004. 910 then adopted 1080's former hot talk format as KOTK. Personalities on "Max" included Don Imus, Rick Emerson, Don & Mike, Tom Leykis and Phil Hendrie. On April 21, 2005, it flipped back to oldies as KKSN, picking up the oldies format after KKSN-FM 97.1 flipped to adult hits as "Charlie FM". On February 15, 2007, KKSN changed their call letters to KTRO; and on March 28, 2007, KTRO-FM changed their format to regional Mexican and changed their call letters to KRYP, and the existing talk format continued on KTRO AM. The station is owned by Entercom but was programmed by Salem Communications. The former program lineup was similar to that found on other Salem stations throughout the United States. On January 5, 2009, the station switched to a simulcast of KWJJ, an FM country music station. The LMA with Salem Communications expired. On May 1, 2009, KTRO switched to ESPN Deportes Radio, a Spanish-language sports talk network. On May 28, 2010, KTRO changed their call letters back to KKSN. The station dropped ESPN Deportes Radio on July 12, 2010 in favor of simulcasting the programming of KNRK-HD2, which airs music from local bands. On September 11, 2013, KKSN changed its call letters to KMTT as part of a warehousing move by Entercom. The former holder of the call letters, 103.7 FM in Seattle, now uses the call letters KHTP. On November 1, 2013, KMTT changed their format from "94/7 too" with local and Northwest music to sports, branded as "Sports 910" with programming from CBS Sports Radio. On September 10, 2015 KMTT switched affiliations from CBS Sports Radio to ESPN Radio and rebranded as "910 ESPN Portland".
