In July 2007, CNN/Money and Money magazine ranked Middleton the best place to live in the United States.
As of the census of 2000, there were 15,770 people, 7,095 households, and 3,980 families residing in the city. The population density was 1,953.2 people per square mile (754.5/km²). There were 7,397 housing units at an average density of 916.2/sq mi (353.9/km²). The racial makeup of the city was 92.08% White, 1.97% Black or African American, 0.45% Native American, 2.66% Asian, 0.03% Pacific Islander, 1.27% from other races, and 1.54% from two or more races. 2.82% of the population were Hispanic or Latino of any race.
There were 7,095 households out of which 27.9% had children under the age of 18 living with them, 45.5% were married couples living together, 8.1% had a female householder with no husband present, and 43.9% were non-families. 34.5% of all households were made up of individuals and 7.2% had someone living alone who was 65 years of age or older. The average household size was 2.21 and the average family size was 2.90.
In the city the population was spread out with 22.7% under the age of 18, 8.7% from 18 to 24, 33.1% from 25 to 44, 25.2% from 45 to 64, and 10.3% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 92.1 males. For every 100 females age 18 and over, there were 88.6 males.
The median income for a household in the city was $50,786, and the median income for a family was $71,514. Males had a median income of $41,070 versus $30,928 for females. The per capita income for the city was $29,464. About 3.1% of families and 5.0% of the population were below the poverty line, including 7.2% of those under age 18 and 2.8% of those age 65 or over.
Since 1990 there has been a population increase of over 20% in the Madison metropolitan area. This has led to Middleton being considered as the western hub of a proposed 13-mile railroad corridor] connecting Middleton's Greenway Station, the University of Wisconsin-Madison campus, downtown Madison, and Madison's far east side.