On January 1, 2008, the town of Westfield incorporated; and Andy Cook was sworn in as Mayor. With recent annexations in southern Washington Township and rapid population growth in areas already occupied by the pre-existing town, the City government estimates Westfield's population to be at roughly 30,000 residents. Because of the growing size of the city, officials are planning a major revamp of the downtown. This would possibly include building a new library and city hall. 
As of 2000 the median income for a household was $52,963; and for a family, $65,208. Males had a median income of $45,388; females, $26,864. The per capita income was $22,160. About 2.3% of families and 4.0% of the population were below the poverty line, including 2.5% of those under 18 years and 3.7% 65 years or over.
As of the census of 2010, there were 30,068 people, 10,490 households, and 8,146 families residing in the town. The population density was 1,120.3 inhabitants per square mile (432.6 /km2). There were 11,209 housing units at an average density of 417.6 per square mile (161.2 /km2). The racial makeup of the town was 90.9% White, 2.2% African American, 0.2% Native American, 2.5% Asian, 2.6% from other races, and 1.6% from two or more races. Hispanic or Latino of any race were 5.8% of the population.
There were 10,490 households of which 47.0% had children under the age of 18 living with them, 64.9% were married couples living together, 9.3% had a female householder with no husband present, 3.4% had a male householder with no wife present, and 22.3% were non-families. 18.0% of all households were made up of individuals and 4.6% had someone living alone who was 65 years of age or older. The average household size was 2.85 and the average family size was 3.27.
The median age in the town was 33.7 years. 31.9% of residents were under the age of 18; 5.9% were between the ages of 18 and 24; 31.6% were from 25 to 44; 23.7% were from 45 to 64; and 6.8% were 65 years of age or older. The gender makeup of the town was 48.9% male and 51.1% female.
According to the 2010 census, the town has a total area of 27.08 square miles (70.1 km2), of which 26.84 square miles (69.5 km2) (or 99.11%) is land and 0.24 square miles (0.62 km2) (or 0.89%) is water.