Until January 20, 1969 the Grand Canyon was not fully safe from flooding and becoming another major man made lake in Arizona. President Lyndon B. Johnson fixed that problem when just before leaving from office he signed into act the creation of Marble Canyon National Monument. The monument played a key role in saving the Grand Canyon, by preventing any future dams from being constructed downstream, potentially flooding the Canyon. Marble Canyon was added to the Grand Canyon in 1975 when the Grand Canyon Enlargement Act was signed into law. The act protected the entire area from Lake Mead to Glen Canyon. Though Johnson protected Marble Canyon late in his presidency, he is one of the main reasons rafters can enjoy the Canyon's world-class waters.