As of the census of 2000, there were 139,750 people, 54,515 households, and 35,979 families residing in the county. The population density was 132 people per square mile (51/km²). There were 64,900 housing units at an average density of 61 per square mile (24/km²). The racial makeup of the county was 94.04% White, 2.18% Black or African American, 0.43% Native American, 0.36% Asian, 0.03% Pacific Islander, 1.73% from other races, and 1.23% from two or more races. 4.22% of the population were Hispanic or Latino of any race. 17.3% were of German, 15.1% Italian, 11.6% Swedish, 10.9% English, 9.3% Polish, 9.2% Irish and 5.6% American ancestry according to Census 2000. 93.0% spoke English and 3.8% Spanish as their first language.

There were 54,515 households out of which 30.50% had children under the age of 18 living with them, 50.90% were married couples living together, 10.80% had a female householder with no husband present, and 34.00% were non-families. 28.10% of all households were made up of individuals and 12.60% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 2.99.

In the county the population was spread out with 24.50% under the age of 18, 10.30% from 18 to 24, 26.30% from 25 to 44, 23.00% from 45 to 64, and 16.00% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 95.20 males. For every 100 females age 18 and over, there were 92.20 males.

The median income for a household in the county was $33,458, and the median income for a family was $41,054. Males had a median income of $32,114 versus $22,214 for females. The per capita income for the county was $16,840. About 9.70% of families and 13.80% of the population were below the poverty line, including 19.30% of those under age 18 and 8.20% of those age 65 or over.

Government

Chautauqua County was governed by a board of supervisors until 1975, when a new county charter went into effect with provisions for a county executive and a 13-seat county legislature.

Chautauqua County Executives Name Party Term
Joe Gerace Democrat January 1, 1975 – May 10, 1983
David Dawson (acting) Democrat 1983 – 1983
John A. Glenzer Republican November 25, 1983 – December 31, 1989
Andrew W. Goodell Republican 1990 – December 31, 1997
Mark W. Thomas Democrat January 1, 1998 – December 31, 2005
Gregory J. Edwards Republican January 1, 2006 –

Most of the county is in the 150th New York State Assembly district, represented by Democrat William Parment, with the exception of the eastern tier of towns, which are in the 149th district represented by Joseph Giglio. The entire county is within the bounds of New York's 27th congressional district (served by Brian Higgins) and the New York State Senate 57th district (served by Catharine Young). Prior to 2003, the county was part of New York's 31st congressional district (now the 29th), but was controversially redistricted out of that district and into what is now the 27th, and was replaced in the 29th district by Rochester suburbs that had never before been part of the district.

Chautauqua County has been a perfect bellwether county since 1980, having correctly voted for the winner of the presidential election in each election; the county missed twice between 1960 and 1976.