Mr. May decided to go down to sewers himself to determine whether there was anything other than an excess of whiskey behind his inspectors' reports of narrow escapes from alligators. That startling description of what he found, given by the man affectionately known as the King of the Sewers and recounted by a journalist, was immortalized in "The World Beneath the City":"The Book Behind the Sewer-Alligator Legend" (NY Times)
Alligators serenely paddling around in his sewers. The beam of his own flashlight had spotlighted alligators whose length, on the average, was about two feet. Some may have been longer. Avoiding the swift current of the trunk lines under major avenues, the beasts had wormed up the smaller pipes under less important neighborhoods, and there Teddy had found them. The colony appeared to have settled contentedly under the very streets of the busiest city in the world...
"These tales had a journalistic background," said Loren Coleman, director and curator of the International Cryptozoology Museum in Portland, Me., who has researched and written about the topic for decades. "Daley's book came along, and it was almost like independent confirmation."
More background at Cryptomundo