At the 2010 census, there were 41,094 people and 15,335 households with an average of 2.5 persons per household in the city. The population density was 887.2 per square mile. There were 16,075 housing units with a homeowner vacancy rate of 1.2% and a rental vacancy rate of 4.6%. The racial makeup of the city was 92.8% White, 1.6% African American, 0.3% Native American, 01.3% Asian, 0.05% Pacific Islander, 2.2% from other races, and 1.8% from two or more races. Hispanic or Latino of any race were 7.5% of the population.
There were 15,335 households of which 30.9% had children under the age of 18 living with them, 65.5% were family households, 49.3% were a husband-wife family, 11.4% had a female householder with no husband present, 4.8% had a male householder with no wife present, and 34.5% were non-families. 30.9% of all households were made up of individuals under 18 years of age and 26.5% of all households are with individuals 65 years and over. The average household size was 2.5 and the average family size was 3.05.
Age distribution was 26.7% under the age of 20, 9.5% from 20 to 24, 22.8% from 25 to 44, 27.4% from 45 to 64, and 13.6% who were 65 years of age or older. The median age was 38.3 years. 48.9% of the population is male whereas 51.1% of the population is female.
The median household income was $53,772, and the per capita income was $26,605. Males had a median income of $38,316 versus $27,459 for females. About 6.9% of families and 9% of the population were below the poverty line, including 16.2% of those under age 18 and 9.5% of those age 65 or over.
As of the 2012 Voter Registration and Party Enrollment information, there are a total 23,348 registered voters in the City of Westfield, with 6,834 Democratic, 4,452 Republican, 11,898 Unaffiliated, and 31 Minor Party associations.
For a complete breakdown of the 2000 census study of the City of Westfield, please see the Westfield Demographic Census Report.