Why were American alligators extinct?

They were never extinct, but they were almost; in the 19th century and early 20th century, they almost died out completely, but then it was declared illegal to hunt them down in America. They are now flourishing and are frequent attractions for tourists.

CORRECTION: The apex of the American Alligator killings was between 1870 and 1970, when it is estimated more than 10 million of them were killed.