What makes the mountains and valleys of Yosemite a national park but the summit of Devils Tower a national monument? The designations have little to do with differences in size or grandeur. (Just last June President Bush created a national monument that spans almost 140,000 square miles [360,000 square kilometers] of ocean and encompasses the Northwestern Hawaiian Islands, an area approximately a hundred times the size of Yosemite.) Rather, the difference between national parks and national monuments has largely political origins. While Congress holds the power to create national parks, the President has the authority to create national monuments.
That executive power goes back a century to the Antiquities Act of 1906, which authorized the President to set aside "historic landmarks, historic and prehistoric structures, and other objects of historic or national interest" as national monuments. While legislators originally intended the Antiquities Act to safeguard Native American archaeological sites in the Southwest from vandalism, the law's loose language also allowed Presidents to bypass the congestion of congressional debate and single-handedly create protected areas.
President Theodore Roosevelt was the first to use this executive power, creating Devils Tower National Monument in 1906. Throughout the 20th century, Presidents have used the national monument designation as a stepping stone to making an area a park. The Grand Canyon, Grand Teton, and Olympic Parks all began as national monuments before Congress approved their national park status.