A Twentynine Palms man has been sentenced to five years in prison for setting a fire that damaged a historical landmark at Joshua Tree National Park. Federal prosecutors say George William Graham was observed watching flames rip through the iconic palm trees in March at the Oasis of Mara in Twentynine Palms and told park rangers he started the fire by igniting a palm frond with a cigarette lighter. The fire burned several palm trees but did not damage any structures. The oasis, which is next to the park’s headquarters, was settled by Native Americans who planted the 29 palm trees that inspired the name of the nearby city of Twentynine Palms. Graham was sentenced to prison Monday and ordered to pay $21,000 in restitution. The 26-year-old is a parolee with a prior arson arrest. His public defender told the judge in June that her client has mental issues.