Rises in the lake level following the damming of Canandaigua Outlet have reduced the island to a small portion of its former land.

Skenoh Island began to form as a sandbar created by the interactions between the sediments carried in Sucker Brook and the counterclockwise currents along the lakeshore.

[2] In 1900, paleontologist John M. Clarke published a paper about the rare oncolites that had long accumulated on the island's north shore.

The disc-shaped white rocks, known locally as "water biscuits", were light yet strong when wet but brittle enough to break by hand when dry.

After the 1899 death of her husband, New York City banker Frederick Ferris Thompson, she had returned to Sonnenberg Gardens, her estate in Canandaigua, and used the fortune she had inherited from him to finance civic improvements.

[11] Throughout the rest of the 20th century, Skenoh Island would face threats greater than those that could be held at bay by making it a protected area.

Damming of Canandaigua Outlet drove up the lake's water level, leaving most of the two spits permanently underwater.

[2] Two years later the state's Department of Environmental Conservation (DEC), which by then managed the land, tried to sell it to the Town of Canandaigua, within whose boundaries the island sat, for $1.