PHOTOS: See The Sweeping American Landscapes Under Review By Trump

President Trump has ordered the Department of the Interior to review all designations of national monuments greater than 100,000 acres created since 1996.

That executive order, which he signed Wednesday, places at least 20 — and as many as 40 — monuments in the government's sights. The areas now under review span a vast range of landscapes — from arid deserts to frozen mountain peaks, from striking craggy vistas to teeming underwater playgrounds.

And, though these monuments were all established roughly in the past two decades, they all have a history more than a century long. That's because all of them owe their existence to the 1906 Antiquities Act, a law signed by President Theodore Roosevelt that makes it a federal crime to destroy or alter ancient artifacts and ruins on federal land.

The act also gives the president the authority to designate national monuments.

More recently, with most large public lands protection bills stalled in Congress, presidents from Bill Clinton to George W. Bush and Barack Obama have used the act as a tool to protect sweeping amounts of federal land mostly in the West.

President Obama's late hour designation of the Bears Ears National Monument in Utah, for instance, protects