"The Antiquities Act of 1906 authorizes the President to proclaim national monuments on federal lands that contain historic landmarks, historic and prehistoric structures, or other objects of historic or scientific interest. The President is to reserve 'the smallest area compatible with the proper care and management of the objects to be protected.' The act was designed to protect federal lands and resources quickly, and Presidents have proclaimed a total of 137 monuments. Congress has modified many of these proclamations and has abolished some monuments. Congress also has created monuments under its own authority. Presidential establishment of monuments sometimes has been contentious--for example, President Franklin Roosevelt's creation of the Jackson Hole National Monument in Wyoming (1943); President Carter's massive Alaskan withdrawals (1978); and President Clinton's establishment of 19 monuments and enlargement of three others (1996-2001). President Obama's designation of nine new national monuments and enlargement of another have renewed controversy over the Antiquities Act. However, the President cited support for his monument designations, most of which had been proposed for protective designations by legislation."
CRS Report for Congress, R41330