We develop a concept of suitable habitat for Glyptemys (Clemmys) muhlenbergii (Bog Turtle) on the Lake Ontario Coastal Plain of central and western New York State and compare it to habitat for this species in other parts of its distribution. At the outset of our studies in 1987, only a single Bog Turtle population was known to survive on the Lake Ontario Plain. We located and visited nine of the 10 historically recorded Bog Turtle sites in northern, central and western New York and completed a survey of 84 selected wetlands in Oswego County, at the eastern end of the Lake Plain. In the course of the study, we confirmed the presence of the Bog Turtle at a site where it was last documented in 1916 and discovered populations at three previously undocumented sites, one of which is now the northernmost recorded site for the species. Bog Turtle habitat on the Lake Ontario Coastal Plain is open-canopy, sedge-dominated medium to rich fens contained within larger wetlands that often include an open pond and extensive Acer rubrum (Red Maple) or Red Maple-Larix laricina (Tamarack) swamp. We discuss events that may have led to the current distribution of Bog Turtle populations in central and northern New York and in western Pennsylvania and implications of this distribution pattern for the conservation of the species.