You might wonder why these specific four men represent the first 150 years of American history. Sculptor Gutzon Borglum chose them carefully to symbolize four essential themes: birth, growth, preservation, and development. George Washington, on the far left, represents the birth of the nation, while Thomas Jefferson nearby symbolizes its growth through the Louisiana Purchase. Abraham Lincoln, on the far right, was chosen for his role in preserving the Union during the Civil War, and Theodore Roosevelt represents the development of the United States as a global power in the twentieth century. The project did not always go according to plan; Jefferson's head was originally intended to be to the right of Washington, but after 18 months of carving, the rock was found to be too weak. They had to blast Jefferson's face off entirely and start over on the other side of Washington. If you look closely at Washington's chest, you will see the only part of the monument where Borglum began carving the torsos, as he originally envisioned full-body figures reaching down to their waists. Funding shortages and the onset of World War Two ultimately meant the project ended with just the faces that you see today.