President Donald Trump, in an executive order signed on Wednesday, ordered Secretary of the Interior Ryan Zinke to conduct a review of all national monuments of 100,000 acres or greater designated since since January 1, 1996. The monuments to be reviewed were all established under sitting U.S. presidents under the Antiquities Act of 1906.

The Trump administration explained that some monument designations by previous administrations were the result of inadequate public outreach and coordination with state, tribal, and local officials.

24/7 Wall St. reviewed the 26 national monuments that the secretary will submit recommendations on within the next 120 days, based on the order’s criteria. The monuments under review range from President Bill Clinton’s designation in 1996 of the Grand Staircase-Escalante National Monument in Utah to most recently, President Barack Obama’s designation last year of the Bears Ears National Monument, also in Utah.

Click here to see the 26 national monuments President Trump wants to shut down.

Unlike national parks, which must be approved by Congress, national monuments can be established unilaterally by sitting presidents as per the Antiquities Act of 1906. All but three of the 19 presidents in office have used this power. Republican President George W. Bush, designated seven national monuments during his tenure, including several that meet the criteria for review under the executive order.

Still, the act is a long-standing sore point for conservatives who often see these designations as federal land grabs and violations of state sovereignty. These designations, critics argue, hinder American enterprise from exploiting potentially valuable land resources.

Conservationists, however, laud the power vested in presidents by the Antiquities Act. These monuments, they argue, are invaluable national treasures that need to be protected from development and destructive resource extraction. These monuments are not just important historical landmarks and wildlife sanctuaries, but they can also contribute to regional economies, by way of tourism.

To determine which national monuments might be shut down by President Trump, 24/7 Wall St. reviewed all national monuments designated after January 1, 1996 with at least 100,000 acres. Some monuments have been expanded since their initial designation. The date and president listed relate to the original designation of the monument rather than the expansion. However, the acreage listed is the total area of the monument, including any area added during an expansion. Most details are from the National Parks Service page on the Antiquities Act of 1906. Some data came from official National Monument websites.

These are the 26 national monuments President Trump wants to shut down.