The United States has 108 protected areas known as national monuments. The President of the United States can establish a national monument by executive order, and the United States Congress can by legislation. The Antiquities Act of 1906 authorized 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.

President Theodore Roosevelt established the first national monument, Devils Tower in Wyoming, on September 24, 1906. He established eighteen national monuments, although only nine still retain that designation. Sixteen presidents have created national monuments since the program began; only Richard Nixon did not. Bill Clinton created the most monuments, nineteen, and expanded three others. Jimmy Carter protected vast parts of Alaska, proclaiming fifteen national monuments, some of which later were promoted to national parks. Barack Obama most recently proclaimed five new national monuments under the Antiquities Act on March 25, 2013.