Homes for sale in Jefferson County. Jefferson County is on the western side of northern New York State, adjacent to the area where the Saint Lawrence River exits Lake Ontario. It is almost due north of Syracuse, and northwest of Utica. The county is at the international border with Canada.
The Black River, which empties into Lake Ontario, is an important stream in the county. Part of the Tug Hill Plateau is in the southern part of the county.
The county also includes nearby islands in the St. Lawrence River, including such large islands as Carleton Island, Grindstone Island, and Wellesley Island.
As of the census of 2000, there were 111,738 people, 40,068 households, and 28,127 families residing in the county. The population density was 88 people per square mile (34/km²). There were 54,070 housing units at an average density of 42 per square mile (16/km²).