The most populous county located in the state of Indiana is Marion County, home of Indianapolis, which, as of 2019, has a population of 954,670. Since the time that the last census was taken in 2010, Marion County has seen an increase in the total population of 5.35%. The next most populous counties in the state of Indiana after Marion County are Lake County (484,411), Allen County (375,351), and Hamilton County (330,086). Of these counties, only Lake County experienced a decline, dropping 2.32% in population. Hamilton County had the most significant growth with a growth rate of 19.38% since the 2010 census.
The county with the lowest population in the state of Indiana is Ohio County, which has a population of 5,844. Since the last census in 2010, Ohio County’s population has seen a decrease of 4.12%. Following Ohio County are Union County (7,047), Warren County (8,263), and Benton County (8,653). All of these counties experienced a decline in the number of residents.
The county with the most rapid population growth was Hamilton County, home of Noblesville, which grew 19.38% to 330,086. Following Hamilton County is Boone County which grew 17.72% and Hendericks County with a population growth rate of 14.46%. The counties with the most significant population loss are Union County (-6.63%), Blackford County (-6.59%), and Pulaski County (-6.43%).