[2] The county lies just south of the border with the Canadian province of Quebec, and to the west of the State of Vermont.

The county is named for George Clinton, the first Governor of New York, who later was elected as Vice President.

Clinton County comprises the Plattsburgh, New York micropolitan statistical area.

[4] The Saranac River flows easterly through the central part of the county, discharging into Lake Champlain at Plattsburgh, and the Great Chazy River flows northeastward through the upper part of the county, discharging into Lake Champlain at Coopersville.

The Ausable River forms a large part of the southern county line.

[5] The county's highest point is Lyon Mountain, in the town of Dannemora, at 3,830 ft (1,170 m) ASL.

[10] In 2006, both Eliot Spitzer and Hillary Clinton carried the county, respectively winning 63% and 64% of the vote.

In 2010, Governor Andrew Cuomo and Senators Chuck Schumer and Kirsten Gillibrand won in the county, each receiving more than 60% of the vote.

The county's Congressional district did not elect a Democrat to Congress until 2009 when Bill Owens defeated Doug Hoffman in the special election to replace John McHugh, who resigned to serve as the Obama Administration's Secretary of the Army.

The special election received nationwide attention due to Hoffman, a third-party candidate and Tea Party favorite, polling higher than the Republican nominee, Dede Scozzafava, which ultimately led to her dropping out of the race and supporting Owens.

The county is also served by Clinton Community College, which is located in the Town of Plattsburgh.

Amtrak's Adirondack Train travels through the county, connecting Montreal to New York City.

Two trains a day (one north and one south) stop in the county in Plattsburgh and Rouses Point.