Adjacent counties

• Hartford County (north)
• New London County (east)
• New Haven County (west)
• Suffolk County, New York (south)

National protected areas

• Silvio O. Conte National Wildlife Refuge (part)
• Stewart B. McKinney National Wildlife Refuge (part)

2000 census

As of the census^[9] of 2000, there were 155,071 people, 61,341 households, and 40,607 families living in the county. The population density was 420 inhabitants per square mile (160/km²). There were 67,285 housing units at an average density of 182 per square mile (70/km²). According to the Census of 2010, the racial makeup of the county was 89.22% White, 4.64% Black or African American, 0.17% Native American, 2.56% Asian, 0.04% Pacific Islander, 1.30% from other races, and 2.06% from two or more races. 4.73% of the population were Hispanic or Latino of any race. 20.4% were of Italian, 14.3% Irish, 11.1% English, 8.9% Polish and 8.2% German ancestry. 91.1% spoke English, 2.6% Spanish, 1.9% Italian, 1.2% French and 1.0% Polish as their first language.

There were 61,341 households, out of which 30.30% had children under the age of 18 living with them, 54.40% were married couples living together, 8.80% had a female householder with no husband present, and 33.80% were non-families. 27.20% of all households were made up of individuals, and 10.00% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 2.98.

In the county, the population was spread out, with 23.20% under the age of 18, 7.30% from 18 to 24, 31.10% from 25 to 44, 24.80% from 45 to 64, and 13.60% who were 65 years of age or older. The median age was 39 years. For every 100 females, there were 95.10 males. For every 100 females age 18 and over, there were 92.10 males.

The median income for a household in the county was $59,175, and the median income for a family was $71,319. Males had a median income of $48,341 versus $35,607 for females. The per capita income for the county was $28,251. About 2.30% of families and 4.60% of the population were below the poverty line, including 4.00% of those under age 18 and 5.90% of those age 65 or over.

2010 census

As of the 2010 United States census, there were 165,676 people, 67,202 households, and 43,743 families living in the county.^[10] The population density was 448.6 inhabitants per square mile (173.2/km²). There were 74,837 housing units at an average density of 202.6 per square mile (78.2/km²).^[11] The racial makeup of the county was 89.2% white, 4.7% black or African American, 2.6% Asian, 0.2% American Indian, 1.3% from other races, and 2.1% from two or more races. Those of Hispanic or Latino origin made up 4.7% of the population.^[10] In terms of ancestry, 24.6% were Italian, 21.2% were Irish, 14.0% were English, 13.5% were German, 11.1% were Polish, and 3.4% were American.^[12]

Of the 67,202 households, 29.4% had children under the age of 18 living with them, 51.9% were married couples living together, 9.4% had a female householder with no husband present, 34.9% were non-families, and 28.2% of all households were made up of individuals. The average household size was 2.39 and the average family size was 2.95. The median age was 43.1 years.^[10]

The median income for a household in the county was $74,906 and the median income for a family was $91,589. Males had a median income of $62,031 versus $50,031 for females. The per capita income for the county was $37,519. About 3.0% of families and 6.1% of the population were below the poverty line, including 6.7% of those under age 18 and 4.3% of those age 65 or over.^[13]

Demographic breakdown by town

City

• Middletown

Towns

Villages are named localities within towns, but have no separate corporate existence from the towns they are in.