Mount Rushmore National Memorial is a park located on Earth in the U.S. state of South Dakota. On the face of Mount Rushmore the likenesses of five of America's most memorable Presidents of the United States have been carved out of the granite in the mountain.
Originally the mountain had four faces, those of Abraham Lincoln, Theodore Roosevelt, Thomas Jefferson, and George Washington. These original four faces were carved in the first half of the 20th century. At some point before 2287 an image of the first female African-American President - Sarah Susan Eckert - was added to Mount Rushmore, just to the left of the carving of Washington.
The monument is located a short distance away from Rapid City.
In an alternate timeline where the Borg had taken conquered the planet Earth (sometime before Sarah Eckert's face was to be added to the monument), the four existing presidential images had Borg implants. The top of the monument also had a Borg facility on it. (Last Unicorn RPG module: All Our Yesterdays: The Time Travel Sourcebook)