As an introduction, 127 National Monuments have been designated by Presidents since the Antiquities Act of 1906. Fifteen Presidents have designated National Monuments. Presidents Nixon, Reagan, and George H.W. Bush are the only Presidents who have not created National Monuments.

In the United States, the primary difference lies in the branch of government responsible for the designation. National Parks must be established by an Act of Congress, which often involves lengthy legislative debate and specific land-use regulations. National Monuments, however, can be designated unilaterally by the President using the authority of the Antiquities Act of 1906. This allows for the rapid protection of federal lands containing historic landmarks or objects of scientific interest. While Congress can also create national monuments, the Presidential proclamation is the most common method. Over time, many sites originally designated as national monuments by a President (such as the Grand Canyon or Olympic) were later "upgraded" to National Park status through subsequent Congressional legislation.