Every year many people visit Mount Rushmore, where the faces of four U.S presidents were carved in granite by sculptor Glutton Borglum and his son, the late Lincoln Borglum. The creation of Mount Rushmore monument took 114 years and a million of dollars. To move the more than 400,000 tons of rock, Borglum hired laid off workers from it the closed down mines in the Black Hills area, He taught these men to dynamite, drill, carve, and finish the granite as they were hanging in midair in his specially devised chairs. During the carving, many changes in the original design had to be made to keep the carved heads free of large fissures that were uncovered. However, not all the cracks could be avoided, so Borglum concocted a mixture of granite dust, white lead, arid linseed oi] to fill them. Every winter, water from melting snows gets into the fissures and l expands as it freezes, making the fissures bigger. Consequently,.every autumn maintenance work is done to refill the cracks.