list of counties in Indiana

There are 92 counties in the U.S. state of Indiana. Each county serves as the local level of government within its borders. Although Indiana was organized into the United States since the Northwest Ordinance in 1787, its land was not always available for settlement. The Vincennes Tract, Clark's Grant and an area known as "The Gore" in southeastern Indiana (resulting from the Treaty of Greenville 1795) existed during the Northwest Territory. The remainder of Indiana land was acquired by Indian Removal Act and purchases by treaty between 1804 and 1840. The largest purchase (called "Delaware New Purchase" or just "New Purchase") resulted from the Treaty of St. Mary's (1818) which acquired about 1/3 of the state in the central portion. All or most of 35 counties were eventually carved from the area. The oldest counties are generally in the south near the Ohio River, whereas newer ones were in the north in territory acquired later. Many of the final counties were formed subsequent to the acquisition and break up of the Big Miami Reserve (encompassing present day Howard County and parts of surrounding counties) between 1834 and 1840. The oldest and newest counties in Indiana are Knox County, created in 1790, and Newton County, created in 1859.

As of the 2025 Census estimates, the population of Indiana was 6,973,333, the average population of Indiana's 92 counties is 75,797, with Marion County as the most populous (992,196), and Ohio County (5,994) the least. 54 counties have 30,000 or more people; 17 counties have populations exceeding 100,000, five of which exceed 250,000; and only five counties have fewer than 10,000 people. The average land area is 396 square miles (1,030 km). The largest county is Allen (657 sq. mi., 1,702 km) and the smallest is Ohio (86 sq. mi., 223 km). According to the Constitution of Indiana, no county may be created of less than 400 square miles (1,000 km), nor may any county smaller than this be further reduced in size, which precludes any new counties.