PIERRE, S.D. (AP) — A man caught trying to climb Mount Rushmore National Memorial has pleaded guilty to charges of trespass and failing to obey a lawful order.

Patrick Marshall, whose last known address is in Chicago, was arrested Monday afternoon as he clambered on loose rock directly below the carvings of four presidents at the monument in western South Dakota.

Assistant U.S. Attorney Mark Salter says 53-year-old Marshall pleaded guilty to the federal charges Tuesday. A federal magistrate fined Marshall $500 and ordered him to pay $50 in court costs.

Mount Rushmore spokeswoman Maureen McGee-Ballinger says visitors and the sculpture were never in any danger. She says similar incidents happen several times a year when people for unknown reasons decide to try to climb the mountain.