National monuments can either be established by Congress though legislation or by the president of the United States through the use of the Antiquities Act.

In the United States, national monuments are created by two primary entities: the President and Congress. Under the Antiquities Act of 1906, the President has the authority to issue a proclamation to designate federal lands as national monuments to protect significant natural, cultural, or scientific features. This power has been used by nearly every president since Theodore Roosevelt to quickly conserve millions of acres. Alternatively, Congress can create national monuments through federal legislation, which involves the standard law-making process of passing a bill through both the House and the Senate for the President's signature. While monuments created by presidents are more common, those created by Congress often receive more complex funding and management frameworks from the start. Once established, these sites are usually managed by the National Park Service (NPS), the Bureau of Land Management (BLM), or the U.S. Forest Service. In 25% of cases, sites that began as presidential monuments (like the Grand Canyon) were later upgraded to "National Park" status by Congress.