Often called "America's best idea,"the creation of the world's first national park at Yellowstone wasn't intended to be a radical new idea by a young nation.
It was a practical solution to a territorial argument. It was supposed to become a state park, but the Yellowstone land was in three territories, none of them yet a state.
"There was an immediate argument between Montana and Wyoming newspapers about who would get the park," Yellowstone National Park historian Lee Whittlesey said. "That is why Congress made it a federal park."
Most members of Congress didn't oppose the Yellowstone legislation because most people hadn't seen the land, Whittlesey said.
"There was no railroad yet and no way to get there. It was incredibly difficult to reach the place," Whittlesey said. "The opposition basically asked, 'Can we farm it? Can we mine it? Oh, we can't? Then we can get rid of it later if we don't like it,' " he said.
That's how Yellowstone National Park became the world's first national park on March 1, 1872.
The creation of other national parks and monuments soon followed, culminating in the creation of the National Park Service on August 25, 1916.
As the National Park Service celebrates its 100th anniversary this year, it now cares for 409 park sites spread over more than 84 million acres (131,250-plus square miles) in all 50 states, the District of Columbia and U.S. territories.
These areas include national parks, monuments, battlefields, military and historical parks, historic sites, scenic rivers, lakeshores, seashores, recreation areas, trails and even the White House.
Visitors are flocking to the parks in record numbers, with more than 305 million visits during 2015, a 12 million visit increase over 2014, according to initial estimates.