(Linda Davidson/THE WASHINGTON POST - The Harriet Tubman Historical Marker at Brodess Farm in Cambridge, Md.)

President Obama defied congressional opposition and designated five new national monuments Monday, using his executive authority to put historic sites and wild landscapes in a half-dozen states off limits to development..

The designations affect three areas managed by the National Park Service, including one honoring abolitionist Harriet Tubman and the Underground Railroad in Maryland and a collection of sites commemorating Delaware as the nation's first state. Obama also used his power under the 1906 Antiquities Act to protect two swaths of land under the Bureau of Land Management’s control: Washington’s San Juan Islands and New Mexico’s Rio Grande del Norte.