Despite looking similar and thriving in comparable habitats, crocodiles and alligators only coexist in one place on Earth: Everglades National Park in South Florida.

Crocodiles and alligators have been around for a long time. There aren't many species alive today that survived the extinction event that wiped out the dinosaurs. Scientists have traced Crocodylomorpha (the group of archosaurs that includes crocodiles, alligators, and their extinct relatives) back to around 145 million years ago, in what is now Europe. 

Some time after that in North America, the group split apart further, with crocodiles being able to tolerate saltwater, while alligatorids (a group including alligators and caimans) cannot. 

"It seems most likely that the ancestors of today’s alligators and crocodiles evolved in North America, and then subsequent to that alligatorids stay more or less within the Americas while crocodiles get everywhere else," Paul Barrett, a palaeontologist at the Natural History Museum in London, explained in a statement. 

"It looks like the ability to cross saltwater bodies has allowed crocodiles to become much more widely dispersed than alligators: crocodiles are found all over the world, including in tropical oceans, whereas alligators are confined to freshwater and unable to reach some areas."

There are two species of crocodilians that live in the United States, the American alligator (Alligator mississippiensis) and the American crocodile (Crocodylus acutus), both adhering to the "just shove the word 'American' in front of it" naming system. American alligators are found throughout the southeastern United States, while American crocodiles inhabit coastal areas of south Florida.

At the northernmost point of the crocodiles' range and the southernmost point of the alligators' range, however, there is crossover in Everglades National Park, where both animals co-exist. The two species live in the park, with Lake Okeechobee providing the freshwater that the alligators need. 

Both species do not enjoy the company of other crocodilians, but have inhabited this same region for some time now. American alligators in the region would have looked the same around 8 million years ago, sharing the space with the now extinct giant crocodile Gavialosuchus americanus.