MOUNT RUSHMORE NATIONAL MEMORIAL, S.D. -- Democrat Barack Obama paid an unscheduled late-night visit to Mount Rushmore Friday, visiting the national memorial at closing time and joking that his ears were too big to ever be included in such a display.

Two days after rival Hillary Rodham Clinton made a campaign stop here, Obama joined a group of reporters and staff members for an after-dark sightseeing visit to the national memorial, where the faces of four presidents are carved into the mountain. South Dakota and Montana hold their primary elections on Tuesday, the final ones in the nation, and Obama was campaigning in both states.

Asked by a reporter if he ever envisioned himself carved into the mountain, he said, "I don't think my ears would fit. There's only so much rock up there."

On her visit, Clinton also batted away reporters' questions about whether she or her husband, former President Clinton, might one day be immortalized there. "Why don't you learn something about the monument?" Clinton said.

Obama said it was his first visit to the landmark.

He did express curiosity about the filming of a chase scene in "North by Northwest," Alfred Hitchcock's 1959 classic starring Cary Grant and Eva Marie Saint that included a death-defying scramble over Rushmore's presidential faces.

"How did they get up there in the first place?" he asked ranger Wesley Jensen.

"They didn't. It was a movie set," Jensen told him.

"Pretty spiffy, isn't it," said the Illinois senator, summing up his overall impressions.