Disney World (The Awful Truth)

In 1936 a nuclear explosion ravished Florida. At the epicenter of the explosion a concentration of radiation so dangerous that any living creature would be instantly mutated into a horrible abomination. This is where Walt Disney himself found a puddle of radioactive sludge where an unsuspecting mouse had fallen in. It's body was contorted so that he now walked on hind legs and had large bloated ears; his face almost seemed to be smiling and Walt was surprised that the mouse could speak! It only said two words.
"Kill me."
The thrilled Walt Disney realized that the radioactive puddle might alter other animals. So, over the years he emptied ducks, dogs, mice, and even the stray raccoon into the dregs of atomic radiation. Not all were as fortunate as the pain racked "Mickey" the mouse.
After the government found this puddle among the wreckage and realized how the media might not like the mutated animals running around Florida. They funded Walt Disney to keep him quiet and built Magic Mountain right over the puddle of goo.
The public would never know.
Now every time anyone rides through Magic Mountain trace radiation sticks with them. So the tourists are slowly filtering the radiation and spreading it across these United States!