The President of the United States can establish a national monument by presidential proclamation, and the United States Congress can do so by legislation. The president's authority arises from the Antiquities Act of 1906, which authorizes the president to proclaim "historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest" as national monuments. read more
Devils Tower was the first declared United States National Monument, established on September 24, 1906, by President Theodore Roosevelt. read more