Long before its hills were bulldozed and its wetlands paved over, Manhattan was an extraordinary wilderness of towering chestnut, oak, and hickory trees, of salt marshes and grasslands with turkey, elk, and black bear—"as pleasant a land as one can tread upon," Hudson reported. Sandy beaches ran along stretches of both coasts on the narrow, 13-mile-long island, where the Lenape feasted on clams and oysters. More than 66 miles of streams flowed through Manhattan, and most of them sheltered a beaver or two—making José's appearance, in Sanderson's eyes, a rare glimpse of the way things used to be.
"You might find it difficult to imagine today, but 400 years ago there was a red maple swamp right here in Times Square," he said one day not long ago, as he waited for the light to cross Seventh Avenue. Dressed in black jeans and a Windbreaker, he didn't look much different from the tourists beside him on the curb. But unlike them, in his mind he was following a trail along a swampy creek that disappeared beneath the entrance to the Marriott Marquis Hotel at the corner of Broadway and West 46th Street. "Just over there was a beaver pond," he said, as a bus rumbled by. "It would have been a good place for deer, wood ducks, and all the other animals associated with streams. Brook trout probably, as well as eels, pickerel, and sunfish. It would have been much quieter, of course, although today's not so bad."
Sanderson conceived the Mannahatta Project one evening in 1999, after buying a coffee-table book of historical maps of the city. A recent transplant to New York from northern California, he was curious about how the city had evolved. "The landscape in Manhattan is so transformed, it makes you wonder what was here before," he said. "There are views in this city where you cannot see, except for a person or maybe a dog, another living thing. Not a tree or a plant. How did a place become like that?"
One map in particular caught his eye: a beautifully colored print from 1782 or 1783 that showed the hills, streams, and swamps as well as roads, orchards, and farms on the entire island—something no other contemporary map had done. More than ten feet long and three feet wide, the map had been created by British military cartographers during the eight-year occupation of New York during the American Revolution. Later called the "British Headquarters Map," it showed the island's topography in unusual detail because British officers needed that information to plan their defense of Manhattan. To Sanderson the map presented a unique opportunity to strip away the city's skyscrapers and asphalt and look at least partway back to the island's original landscape.