Hamilton County, Indiana

Hamilton County is a county in the U.S. state of Indiana. The 2020 United States census recorded a population of 347,467. The county seat is Noblesville.

Hamilton County is part of the Indianapolis metropolitan area. Since the beginning of the 21st century, Hamilton County has been the second most populous county in Central Indiana. It is the highest-income county in Indiana, and one of the highest-income counties in the United States.

Hamilton County's roots are in agriculture. However, after World War II, development in Indianapolis grew northward, and cities/towns in the southern and central part of Hamilton County developed as suburbs. Residential and commercial development have replaced many farm fields, although the county's northern part remains largely agricultural. In the first decades of the 21st century, the county is one of the fastest-growing counties in the United States. According to 2007 estimates by the US Census, the county's population increased from 182,740 in 2000 to an estimated 261,661 in 2007, making it the fastest-growing county of Indiana's 92. As of the 2010 census, Hamilton County surpassed St. Joseph County in population, making it the state's fourth most populous.

In 2020, Hamilton County was home to three of the state's 20 largest cities and towns: Carmel (5th), Fishers (6th), and Noblesville (12th).

Geist and Morse reservoirs are two man-made lakes in Hamilton County that offer boating, fishing, and waterfront living.

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. The city of Carmel in southwestern Hamilton County was designated CNN Money's top place to live in 2013 and in 2017, the city of Fishers was named best place to live.

The land containing Hamilton County was brought into the possession of the United States by the Treaty of St. Mary's in 1818. William Conner was the first white settler in the county. In the summer of 1822, after realizing there were enough settlers in the area, Conner and other settlers applied to the Indiana Legislature for a charter authorizing them to become a separate and independent county under Indiana law. The application was presented to the 1822–23 session of the Indiana General Assembly, and the act was passed and approved by the governor on January 8, 1823. The act took effect on the first Monday in April (April 7), 1823. The county commissioners first met on May 5, 1823, at Conner's house; it also served as the county circuit courthouse. The county was named for Alexander Hamilton, the first secretary of the US treasury.

2,165 soldiers from Hamilton County served in the Civil War. The last veteran residing in the county died in 1942.