The second installment of the National Treasure series, the story involves treasure hunter Ben Gates (Cage) trying to uncover the truth behind the 1865 assassination of President Abraham Lincoln. The complicated plot takes them to Mount Rushmore National Memorial. Apparently President Calvin Coolidge had the four faces carved to hide a secret City of Gold.
Once filming began, the producers were so taken with the beauty of the Black Hills and the friendliness of the people that the crew stayed on to film more scenes than originally planned.
One memorable interaction story comes from Jim Manwell of the National Park Service staff: During filiming, the staff was directed not to approach the actors. But between takes, Nicolas Cage marked up to Manwell and said, "How long did it take to grow that beard?" Manwell's beard is famous at Mount Rushmore. It reaches down to his elbows (he hasn't shaved since 1980) and is carefully manicured.
What liberties did they take with the georgraphy? The stars somehow managed to find a beautiful alpine lake right behind the mountain carving. That beautiful lake is actually Sylvan Lake, but it's not behind Mount Rushmore.
By the way, you won't find James Mason's house back there either. (Hint: "North by Northwest.") Keystone has hosted a number of filmmakers and televisions shows over the years. Mount Rushmore offers a dramatic backdrop that filmmakers find it irresistible.