The area of Ohio was part of the original territory of the United States, being part of lands ceded by four states to the United States and designated in 1787 as the "Territory northwest of the River Ohio." It also included the area known as the Connecticut Western Reserve, which was not ceded by Connecticut to the United States until 1800. Ohio Territory was organized on April 30, 1802, from the Northwest Territory, with generally the same boundary as the present state. Ohio was admitted to the Union on February 19, 1803, as the 17^th state. Ohio acquired legal title to the area known as the Toledo Strip when Michigan ceded its claim in 1836.

Although not yet legally established as a separate entity, census data for Ohio are available beginning with the 1800 census. The 1800 census population for Michigan includes the population of a small area in present-day Ohio. The 1800 population of the legally established Northwest Territory (of which Ohio was a part) was 45,916. For an explanation of the revision to the 1800 population of Ohio, see Richard L. Forstall, Population of States and Counties of the United States: 1790-1990, Washington, DC: U.S. Government Printing Office, 1996, page 126.

Data for the legally established state of Ohio are available beginning with the 1810 census.

METROPOLITAN AND MICROPOLITAN STATISTICAL AREAS AND RELATED STATISTICAL AREAS

Ohio has 16 metropolitan statistical areas, 29 micropolitan statistical areas, and 9 combined statistical areas.

COUNTIES

There are 88 counties in Ohio.  Each county is governed by a board of county commissioners.

COUNTY SUBDIVISIONS

There are 1,604 county subdivisions in Ohio known as minor civil divisions (MCDs). There are 1,324 townships of which are all functioning governmental units except for unpopulated Wayne township in Montgomery County and 15 townships that are wholly within the boundaries of an incorporated place. (Any township that is entirely within an incorporated place is nonfunctioning.) A nonfunctioning township is created when a place that is independent of townships annexes area from an adjacent township, but does not remove the annexed area from the original township. Where this occurs, the Census Bureau creates a fictitious township, generally named after the incorporated place, that conforms to the area that is independent of any township. There are 258 incorporated places that are wholly or partially independent of any county subdivision creating 274 entities that the Census Bureau treats as equivalent to county subdivisions. In addition, there are five undefined MCDs that represent water area.

PLACES

Ohio has 1,204 places; 938 incorporated places and 266 census designated places (CDPs). The incorporated places consist of 250 cities and 688 villages. There are 179 cities and 79 villages that are entirely or partially independent of the surrounding county subdivisions creating 192 and 82 county subdivisions, respectively. Of the 179 cities, 13 cities are partially independent, that is, the city is independent of county subdivisions in one county and dependent in another. These 13 cities are Alliance, Columbus, Crestline, Dublin, Fostoria, Galion, Huber Heights, Middletown, Rittman, Sharonville, Union, Vermilion, and Westerville. Lastly, there are 11 cities and three villages that contain an entire nonfunctioning township and also are dependent within a governmental township. These places are Celina, Columbus, Delaware, Dublin, Galion, Lancaster, Mansfield, Medina, Reynoldsburg, Union, and Westerville cities; and Creston, Seville, and Sunbury villages. Lastly, there are five cities that can legally exist in only one township but are not coextensive—Gahanna, Geneva, Springboro (Warren County portion only), Troy, and Worthington cities.

Cities have a minimum population of 5,000 and villages have a population less than 5,000 and are classified based on Census Bureau counts as certified by the Ohio Secretary of State.

CENSUS TRACTS/BLOCK GROUPS/BLOCKS

Ohio has 2,952 census tracts, 9,238 block groups, and 365,344 census blocks.

CONGRESSIONAL DISTRICTS

For the 111^th Congress (January 2009-January 2011), Ohio had 18 congressional districts.  For the 113^th Congress (January 2013-January 2015), Ohio has 16 congressional districts as a result of reapportionment based on the 2010 Census.

SCHOOL DISTRICTS

Ohio has 616 unified school districts.

STATE LEGISLATIVE DISTRICTS

There are 33 state senate districts and 99 state house districts in Ohio.  In addition, there is one state house district undefined and one state senate district undefined that encompass water area.

URBAN AREAS

Ohio has 155 urban areas; 18 urbanized areas and 137 urban clusters.

ZIP CODE TABULATION AREAS

There are 1,197 ZIP Code tabulation areas (ZCTAs) in Ohio.

¹  Source:  U.S. Department of Commerce, Bureau of the Census, Fourteenth Census of the United States, 1923
²  Source:  U.S. Census Bureau, recomputation for historical county level data which relied upon aggregate county level population data with an estimated county centroid resulting in a possible error of up to one mile.
³  Source:  U.S. Department of Commerce, Bureau of the Census, Centers of Population for States and Counties, 1974
⁴  Source:  U.S. Census Bureau, Geography Division, recomputation from archived national block group/enumeration area data resulting in a possible error of up to 1,000 feet.
⁵  Source:  U.S. Census Bureau, Geography Division, recomputation from archived national block group data resulting in a possible error of up to 1,000 feet.
⁶  Source:  U.S. Census Bureau, computation from national block-level data