The nation's list of national monuments—places of "historic or scientific" interest—has grown by five. On Monday, President Obama added five sites to the 103 previously enshrined.

The newcomers range from an ancient canyon in New Mexico to a 480-acre (194-hectare) property in Maryland where the courageous abolitionist Harriet Tubman helped to free runaway slaves.

National monuments do not have the same status as national parks, but once a site is designated as a national monument, Congress has the authority to designate it a national park. Nearly half of today's national parks began as national monuments.

Under the Antiquities Act, a President can protect public land without waiting for Congress to pass legislation. The first President to use this prerogative was Theodore Roosevelt, who in 1906 protected the flat-topped volcanic formation Devils Tower in Wyoming. Since then, 16 presidents have established national monuments, with President Clinton topping the charts with 22 establishments or expansions.

President Obama's action marks the culmination of years of work by conservationists, cultural organizations, and local citizens to save slices of American history, preserve native fauna and flora, and boost local economies. Here are the country's newest protected landscapes:

The Rio Grande del Norte National Monument

What: Largest of the new national monuments, this 236,000-acre site includes a 200-foot-deep canyon carved by the Rio Grande in New Mexico. The landscape also includes the Taos Plateau, the largest volcanic field within the Rio Grande Rift, and Ute Mountain, a freestanding former volcano rising nearly 3,000 feet above the surrounding plains. Eagles, hawks, and falcons soar and nest along the gorge, and bears, cougars, elk, and bighorn sheep roam the land.

Backstory: The Rio Grande's cultural traditions span at least 11,000 years. "Petroglyphs scattered throughout the area are witness to the people who have been part of the Rio Grande for so many generations," said John Olivas, traditional community organizer for the New Mexico Wilderness Alliance. The Rio Grande was also one of the first rivers to be designated by Congress as a Wild and Scenic River in 1968.

The Harriet Tubman Underground Railroad National Monument

What: Ribboned by fresh and saltwater marshes, this 480-acre expanse located on Maryland's Eastern Shore tells a central piece of Harriet Tubman's story. It includes the plot of land where lived Jacob Jackson, a former neighbor and free black who used coded messages from Tubman to help free her brothers on Christmas Day. "The landscape still looks much as it did during their time," said Ann Simonelli, spokesperson for The Conservation Fund.

Backstory: Tubman fled her owner's farm in Dorchester County, Maryland, by hiding in cornfields and wading through swamps until she reached freedom in the North. She returned to the Eastern Shore 13 times to free family, friends, and hundreds of fugitive slaves. "Even today, many Americans can relate to Harriet Tubman's story of empowerment and self-fulfillment, and the way she refused to accept the unfair circumstances of her early life," said Simonelli.

First State National Monument

What: A scenic riverside landscape and a cluster of historic buildings—the Old Sheriff's House, New Castle Green, Dover Green, and Old New Castle Courthouse (which is the oldest continuously used chamber of justice in the country)—shed light on Delaware's early settlement and the locals who played an important role in American independence. The largest part of the site, the 1,100-acre (445-hectare) Woodlawn property, lies on the banks of the Brandywine River between Wilmington, Delaware, and Philadelphia, Pennsylvania. (See photographs of the new monument in the April issue of National Geographic.)

Backstory: Delaware, the first state to ratify the U.S. Constitution, is also the last to gain a national monument or park. "If you're the first state, it means you've waited a long time," said Blaine Phillips, senior vice president and mid-Atlantic regional director for The Conservation Fund, which helped preserve the Woodlawn tract along the Brandywine River. The river powered the paper mills that supplied materials for Benjamin Franklin's print shop—which may have been the source for the paper on which the Declaration of Independence was written.

The largest battle of the Revolutionary War, in which British forces defeated General George Washington's troops, was fought a short distance upstream in Pennsylvania. Today deer and an occasional bald eagle can be spied amid oak trees and rolling farmland, where long ago the Lenape tribe hunted. "You can get a sense of everything that's happened when you're on the property," said Phillips. "It brings all the threads together to tell those stories." (Related: Delaware Gets Its First National Monument.)

The San Juan Islands National Monument

What: The San Juan archipelago along the coast of Washington state attracts some 75,000 visitors a year who come to camp, hike, and watch whales that swim near shore. Although the new national monument protects only one percent of the island chain, "It's an undeveloped one percent that is pretty dear to us," said Tom Reeve, a member of the Islanders for the San Juan Islands National Monument.

Backstory: The 1,000 acres that make up the monument are spread over 75 sites, ranging from parcels of islands to small reefs. Some sites harbor ancient trees and rare plants, while others provide refuge for harbor seals, sea lions, and migratory songbirds. Old lighthouses, historic homesteads, and Native American and settler fishing sites remain today. Native Americans set fire to the lowlands to cultivate a local plant, and these rare coastal prairies form part of the cultural landscape.

The Charles Young Buffalo Soldiers National Monument

What: This site in Wilberforce, Ohio, preserves the home of Charles Young, the first African American to rise to the rank of colonel and the first superintendent of a national park. The large house with its stained glass windows was built in 1864 and has been a National Historic Landmark since 1974.