While serving as mayor of Kenai, Alaska, in 1980, Gilman was elected to a seat in the state senate vacated by the retirement of Senate President Clem Tillion.[4] In April 1984, Gilman stated that he did not intend to run for reelection to the seat.[5] In December 1984, the Alaska Environmental Lobby scored the departing Gilman as tied with two other members (one Republican and one Democrat) as the lowest-rated member of the state senate on their evaluation of environmental issues.[6]
Gilman again ran for mayor of Kenai in 1987, and was "considered the heavy favorite" in the race.[7] After winning that contest, he was also appointed to the Pacific Northwest Hazardous Waste Advisory Council by Alaska Governor Steve Cowper.[8] As mayor, in 1992 he traveled to Sakhalin Island in the Russian Far East to meet with Russian officials and compare efforts to develop oil and gas reserves with those in Alaska.[9] In 1996, still serving as mayor, he expressed concern with opposition by Governor Tony Knowles to federal plans to allow offshore oil and gas drilling in Cook Inlet.[10]