Sagadahoc County is part of the Portland–South Portland–Biddeford, Maine Metropolitan Statistical Area.
As of the census of 2000, there were 35,214 people, 14,117 households, and 9,641 families residing in the county. The population density was 139 people per square mile (54/km²). There were 16,489 housing units at an average density of 65 per square mile (25/km²). The racial makeup of the county was 96.49% White, 0.92% Black or African American, 0.31% Native American, 0.63% Asian, 0.06% Pacific Islander, 0.38% from other races, and 1.21% from two or more races. 1.11% of the population were Hispanic or Latino of any race.
There were 14,117 households out of which 33.20% had children under the age of 18 living with them, 54.60% were married couples living together, 9.60% had a female householder with no husband present, and 31.70% were non-families. 25.20% of all households were made up of individuals and 9.30% had someone living alone who was 65 years of age or older. The average household size was 2.47 and the average family size was 2.96.
In the county the population was spread out with 25.80% under the age of 18, 6.60% from 18 to 24, 30.50% from 25 to 44, 24.90% from 45 to 64, and 12.30% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 96.30 males. For every 100 females age 18 and over, there were 93.10 males.
The median income for a household in the county was $41,908, and the median income for a family was $49,714. Males had a median income of $34,039 versus $24,689 for females. The per capita income for the county was $20,378. About 6.90% of families and 8.60% of the population were below the poverty line, including 12.20% of those under age 18 and 6.40% of those age 65 or over.
22.0% were of English, 11.6% Irish, 11.1% French, 10.6% United States or American, 8.0% French Canadian and 7.3% German ancestry according to Census 2000. 96.1% spoke English and 2.2% French as their first language.