The first national monument in the United States was created by President Theodore Roosevelt on September 24, 1906. Using the power granted to him by the newly passed Antiquities Act of 1906, Roosevelt proclaimed Devils Tower in Wyoming as a protected site. He took this action to preserve the "noble and unique" geological formation, a massive igneous intrusion that rises 1,267 feet above the surrounding terrain. Roosevelt was a staunch conservationist and believed that the President should have the authority to quickly protect landmarks of historical or scientific interest without waiting for lengthy Congressional approval. Following Devils Tower, he went on to establish 17 more national monuments during his presidency, including El Morro and Muir Woods. This established a powerful precedent that has allowed subsequent presidents to protect millions of acres of land, ensuring that sites of cultural and geological significance, such as the Grand Canyon (which Roosevelt first protected as a monument), are preserved for future generations.