In the United States, a national monument is a protected area created by proclamation of the president of the United States or by act of Congress. National monuments protect a wide variety of natural and historic resources, including sites of geologic, marine, archaeological, and cultural importance. The Antiquities Act of 1906 established the national monument designation and gave presidents the power to proclaim the creation of a national monument from any area owned or controlled by the federal government. In contrast, national parks in the U.S. must be created by Congressional legislation. Some national monuments were first created by presidential action and later designated as national parks by congressional approval.