Recently, in a story about the Okefenokee swamp that the Florida-Georgia state line, we noted that it's a true swamp, unlike the more famous Everglades that cover a lot of South Florida.

In fact, Everglades National Park could be called the world's river. It's a vast, extremely slow-moving of water — 180 kilometers (112 miles) wide and no more than a meter deep in most places — stretching all the way from the of Miami on the Atlantic Coast across to Naples on the Gulf of Mexico.

You could call the glades a River of Grass, too: yellow sawgrass that can slice you open

The Everglades were once a formidable frontier. When the United States was pushing Spain out of Florida in the 19th Century, its fiercest was a band of Seminole Indians who harbored escaped U.S. criminals and southern slaves in the Everglades on dry patches of ground called .

In the early 20th Century, when Miami, now a great international city, had only 1,600 residents, nobody could figure out how to the Everglades or overcome the of mosquitoes that brought yellow fever and attacked work crews who tried to lay railroad ties or build towns.

Over the years, though, engineers solved the problem, and the edges of the great River of Grass were steadily drained for housing developments, canals, and roads. Sometimes the results were , as vegetation dried and caught fire, and ditches away fresh water.

Wildlife has also been threatened as the glades . The National Park Service estimates that the number of birds has declined from a quarter of a million in the 1930s to fewer than 20,000 today.

But you'll still see plenty of alligators. They sun themselves along the old, two-lane state road through the Everglades, which may be but are still an awesome sight. There's nothing like them, anywhere in the world.