Together with surrounding communities, the Fond du Lac metropolitan area was, according to the 2000 census, home to 57,479 people. The city forms the core of the United States Census Bureau's Fond du Lac Metropolitan Statistical Area, which includes all of Fond du Lac County (2000 population: 97,296), and which, when combined with the 'Beaver Dam (city), WI Micropolitan Statistical Area', form the larger 'Fond du Lac-Beaver Dam, WI Combined Statistical Area'. It was named the safest metropolitan area in the United States in the 2006 edition of City Crime Rankings by Quinto Press.
Fond du Lac is the larger principal city of the Fond du Lac-Beaver Dam CSA, a Combined Statistical Area that includes the Fond du Lac metropolitan area (Fond du Lac County) and the Beaver Dam micropolitan area (Dodge County), which had a combined population of 183,193 at the 2000 census.
As of the census of 2000, there were 42,203 people, 16,638 households, and 10,282 families residing in the city. The population density was 2,501.3 people per square mile (965.9/km²). There were 17,519 housing units at an average density of 1,038.3/sq mi (401.0/km²). The racial makeup of the city was 93.59% White, 1.86% Black or African American, 0.51% Native American, 1.52% Asian, 0.01% Pacific Islander, 1.27% from other races, and 1.25% from two or more races. 2.92% of the population were Hispanic or Latino of any race.
There were 16,638 households out of which 30.6% had children under the age of 18 living with them, 48.4% were married couples living together, 9.8% had a female householder with no husband present, and 38.2% were non-families. 30.9% of all households were made up of individuals and 12.5% had someone living alone who was 65 years of age or older. The average household size was 2.38 and the average family size was 3.00.
In the city the population was spread out with 24.2% under the age of 18, 10.7% from 18 to 24, 29.4% from 25 to 44, 20.4% from 45 to 64, and 15.3% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 88.7 males. For every 100 females age 18 and over, there were 84.1 males.
The median income for a household in the city was $41,113, and the median income for a family was $50,341. Males had a median income of $35,682 versus $22,492 for females. The per capita income for the city was $18,996. About 4.6% of families and 7.5% of the population were below the poverty line, including 7.9% of those under age 18 and 8.9% of those age 65 or over.