The history of Letchworth State Park reaches back almost ten thousand years. It begins when the last great ice sheet began to melt, allowing the ancient Genesee River to continue its endless journey to the North. As it began the long task of cutting the remarkable gorges at Portage and Mt. Morris, the first inhabitants of the land came to live along its banks.
These first inhabitants are known by the Native people as the "Old Ones". The first Old Ones followed the great Mastodons (such as the Pike Mastodon found in the Park's Museum) and other animals to the Valley when it still resembled an arctic tundra. Then as the landscape warmed and changed, these Paleo-people, as the archaeologists know them, adapted to new ways of life. This new way of life became known as the "archaic stage". Artifacts from this era of the Park history have been found throughout the Valley. Eventually the nomadic hunting and gathering gave way to a more settled life based upon the Three Sisters - corn, beans, and squash.
It was these Woodland People who became the O nodowa'ga, or the Seneca People. Although they, like their ancestors, had long hunted and fished along the Genesee, it was not until the late 1600's that Seneca villages appeared in the part of the Valley they called "Sehgahunda", or the "Vale of Three Falls" (see Seneca Villages in Letchworth Park).
The Seneca were part of the Hodenausanee or Iroquois League. Their communities along the Genesee marked the Western Door to the great symbolic longhouse which they shared with the Cayuga, Onondaga, Oneida, Mohawk, and other tribes willing to join the Great Peace. During the Revolutionary War, these western villages became the targets of an American invasion force.
The main army under the command of Generals' Sullivan and Clinton never entered the present boundaries of the Park, passing through the Valley just to the east. But the villages became havens for refugees from destroyed villages. One group of these survivors was Dehgewanus and her family.
Dehgewanus was the Seneca name of the captive, Mary Jemison, the "White Woman of the Genesee". She and her children found shelter on the Gardeau Flats. Over the next sixty years Dehgewanus would witness the coming of the white man and the end of Sehgehunda.
In 1797 a treaty was held in Geneseo New York between the Seneca and the white settlers. At the Treaty of Big Tree the Seneca sold much of Western New York, setting aside reservations for their use. Two of these were in the Park - Squawkie Hill, at the present day Mt. Morris Dam, and Gardeau, where the Jemison family lived.
The Gardeau Reservation was sold in 1823, and Squawkie Hill passed into white man hands three years later. Dehgewanus, who had maintained title so some of the Gardeau Flats, sold her remaining lands in 1831 and moved to the Buffalo Creek Reservation where she died in 1833.
All the lands that once had been Sehgehunda, were now in the hands of white pioneers.