Hamilton County is a county located in the U.S. state of Indiana. Census 2010 recorded a population of 274,569. The county seat is Noblesville.Hamilton County is included in the Indianapolis-Carmel-Anderson, IN Metropolitan Statistical AreaHamilton County’s roots are in agriculture. However, after World War II, Indianapolis grew north and towns in the southern part of the county developed as suburbs. Many farm fields have been replaced by both residential and commercial development.