List of national monuments of the United States

The United States has 129 protected areas known as national monuments. 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 allows the president to proclaim "historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest" as national monuments. Concerns about protecting mostly prehistoric Indian ruins and artifacts—collectively termed antiquities—on western federal lands prompted the legislation. Its purpose was to allow the president to quickly preserve public land without waiting for legislation to pass through an unconcerned Congress. The ultimate goal was to protect all historic and prehistoric sites on U.S. federal lands, and it has resulted in designation of a wide variety of ecological and historical sites. 
President Theodore Roosevelt established the first national monument, Devils Tower in Wyoming, on September 24, 1906. He established 18 national monuments, although only nine still retain that designation. Seventeen presidents have created national monuments under the Antiquities Act since the program began; only Richard Nixon, Ronald Reagan, and George H. W. Bush did not. Bill Clinton created 19 and expanded three others. Jimmy Carter protected vast parts of Alaska, proclaiming 15 national monuments, some of which later were promoted to national parks. President Barack Obama created or expanded 34 national monuments by proclamation, the most of any president, with over half a billion acres of public land and water protected.
National monuments are located in 32 states, the District of Columbia, the Virgin Islands, American Samoa, the Minor Outlying Islands, and the Northern Mariana Islands. Arizona and California have the most national monuments, each with 18, followed by New Mexico with 13. At least seventy-four national monuments protect places of natural significance, including nineteen primarily for their geological features, eight marine sites, and eight volcanic sites. At least sixty-two national monuments protect historic sites, including twenty-seven associated with Native Americans, nine relating to African American history, and ten forts. Four have been designated World Heritage Sites. With the variety of resource types there is significant variation in the size of national monuments; the median size is roughly . The five largest national monuments are all oceanic marine sites that protect waters and submerged lands where commercial fishing is prohibited. 
Many have been redesignated as national parks or another status by Congress, while others have been transferred to state control or disbanded.
Management by federal agencies.
Eight federal agencies in five departments manage the 129 current U.S. national monuments. Of these, 114 monuments are managed by a single agency, while 15 are co-managed by two agencies. One of the NPS's national monuments, Grand Canyon-Parashant, is not an official unit because it overlaps with Lake Mead National Recreation Area. Management practices vary across agencies and sites according to their missions, the size or type of protected place, and legal authorization. Generally, hunting, fishing, and extraction of resources are prohibited.