Hamilton County's roots are in agriculture. However after World War II, Indianapolis grew north and the county developed as a suburb. Many farm fields have been replaced over the past couple decades by both residential and commercial development.
Today, the county is one of the fastest-growing counties in the nation. According to 2007 estimates by the U.S. Census, the County's population jumped from an estimated 182,740 in 2000 to 261,661 in 2007, 30% of the state's total population increase from between 2000 and 2007. It is the fastest growing county in Indiana out of 92. In 2006, Hamilton County was the 18th fastest-growing county in the nation (out of 3,141) based on census estimates between 2000 and 2005. In 2008, it was the 23rd fastest-growing county in the nation based on census estimates between 2000 and 2007. Recently, Hamilton County surpassed St. Joseph County in population, making it the fourth most populous in the state.
In 2007, Hamilton County was home to 3 of the state's 20 largest cities. Carmel (8th), Fishers (6th), and Noblesville (19th). All three are expected to move up in the rankings by 2010.
Geist and Morse Reservoirs are two man-made lakes in Hamilton County that offer residents and visitors recreational opportunities, such as boating, fishing and waterfront living. Today, Hamilton County is often called the playground of Indianapolis as many parks, museums, venues and recreational spots have become very popular amongst Indianapolis residents.
The median household income of Hamilton County is more than $82,000, making it the most affluent county in Indiana. In June 2008 Hamilton County was named America's Best Place to Raise a Family by Forbes.com due to its strong economy, affordable living, top ranked schools, and close proximity to Indianapolis.
As of the census of 2000, there were 182,740 people, 65,933 households, and 50,834 families residing in the county. The population density was 459 people per square mile (177/km²). There were 69,478 housing units at an average density of 175 per square mile (67/km²). The racial makeup of the county was 94.38% White, 1.54% Black or African American, 0.17% Native American, 2.44% Asian, 0.04% Pacific Islander, 0.54% from other races, and 0.90% from two or more races. 1.59% of the population were Hispanic or Latino of any race. 26.3% were of German, 13.0% American, 12.5% English and 11.2% Irish ancestry according to Census 2000.
There were 65,933 households out of which 43.70% had children under the age of 18 living with them, 67.50% were married couples living together, 7.00% had a female householder with no husband present, and 22.90% were non-families. 18.60% of all households were made up of individuals and 5.00% had someone living alone who was 65 years of age or older. The average household size was 2.75 and the average family size was 3.16.
In the county the population was spread out with 30.80% under the age of 18, 5.60% from 18 to 24, 34.90% from 25 to 44, 21.20% from 45 to 64, and 7.50% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 96.80 males. For every 100 females age 18 and over, there were 93.50 males.
The median income for a household in the county was $71,026, and the median income for a family was $80,239 (these figures had risen to $81,297 and $93,900 respectively as of a 2007 estimate). Males had a median income of $56,638 versus $34,807 for females. The per capita income for the county was $33,109. About 2.00% of families and 2.90% of the population were below the poverty line, including 2.80% of those under age 18 and 3.80% of those age 65 or over.