|OH State Facts|
|Territory: Jul 13, 1787 (NW)|
|Statehood: Mar 1, 1803|
|Borders: PA, WV, KY, IN and MI|
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Today’s Ohio counties did not always exist in the present form. They went through many different changes in the space of a few short years. Ohio Counties were first formed while part of the Northwest Territory, and after that the Ohio Territory.
Ohio Territorial Counties
The old Northwest Territory originally included areas previously known as Ohio Country and Illinois Country. As Ohio prepared for statehood, the Indiana Territory was created, reducing the Northwest Territory to approximately the size of present-day Ohio plus the eastern half of the Lower Peninsula of Michigan and the eastern tip of the Upper Peninsula.
Nine Ohio counties existed at the time of the Ohio Constitutional Convention in 1802. The State of Ohio entered the union as the 17th state on March 1, 1803.
Ohio Counties Today
Fun Facts about Ohio Counties
Counties by Year
- Washington County was the original county created on July 27, 1788.
- Noble County was the last county created on April 1, 1851.
County Size Facts
- Ashtabula County (702 sq mi) is the largest county in Ohio.
- Lake County (228 sq mi) is the smallest county in Ohio.
County Population Facts
- Vinton County (13,435) is the least populated county in Ohio.
- Franklin County (1,264,518) is the most populated county in Ohio.
Ohio City Facts
Ohio’s 10 largest cities (2010) are:
- Columbus (860,090) is in Delaware, Fairfield, Franklin and Pickaway Counties
- Cleveland (389,521) is in Cuyahoga County
- Cincinnati (298,165) is in Hamilton County
- Toledo (281,031) is in Lucas County
- Akron (197,859) is in Summit County
- Dayton (141,003) is in Montgomery County
- Parma (81,601) is in Cuyahoga County
- Canton (73,007) is in Stark County
- Youngstown (66,982) is in Mahoning County
- Lorain (64,097) is in Lorain County
Boundary Changes of Ohio Counties from 1788-1888
This Interactive Map of Ohio Counties show the historical boundaries, names, organization, and attachments of every county, extinct county and unsuccessful county proposal from 1788 to 1888.
List of Ohio Counties
|County||Date Formed||Parent County||County Seat|
|Adams||1797||Hamilton County||West Union|
|Ashland||1846||Wayne, Richland, Huron, and Lorain Counties||Ashland|
|Ashtabula||1807||Trumbull and Geauga Counties||Jefferson|
|Auglaize||1848||Allen, Mercer, Darke, Hardin, Logan, Shelby, and Van Wert Counties||Wapakoneta|
|Belmont||1801||Jefferson and Washington Counties||St. Clairsville|
|Brown||1818||Adams and Clermont Counties||Georgetown|
|Carroll||1833||Columbiana, Stark, Harrison, Jefferson, and Tuscarawas Counties||Carrollton|
|Champaign||1805||Greene and Franklin Counties||Urbana|
|Clark||1818||Champaign, Madison, and Greene Counties||Springfield|
|Clinton||1810||Highland and Warren Counties||Wilmington|
|Columbiana||1803||Jefferson and Washington Counties||Lisbon|
|Coshocton||1810||Muskingum and Tuscarawas Counties||Coshocton|
|Defiance||1845||Williams, Henry, and Paulding Counties||Defiance|
|Erie||1838||Huron and Sandusky Counties||Sandusky|
|Fairfield||1800||Ross and Washington Counties||Lancaster|
|Fayette||1810||Ross and Highland Counties||Washington Court House|
|Franklin||1803||Ross and Wayne Counties||Columbus|
|Fulton||1850||Lucas, Henry, and Williams Counties||Wauseon|
|Gallia||1803||Washington and Adams Counties||Gallipolis|
|Greene||1803||Hamilton and Ross Counties||Xenia|
|Guernsey||1810||Belmont and Muskingum Counties||Cambridge|
|Hamilton||1790||One of the original counties||Cincinnati|
|Harrison||1813||Jefferson and Tuscarawas Counties||Cadiz|
|Highland||1805||Ross, Adams, and Clermont Counties||Hillsboro|
|Hocking||1818||Athens, Ross, and Fairfield Counties||Logan|
|Holmes||1824||Coshocton, Wayne, and Tuscarawas Counties||Millersburg|
|Huron||1809||Portage and Cuyahoga Counties||Norwalk|
|Jackson||1816||Scioto, Gallia, Athens, and Ross Counties||Jackson|
|Knox||1808||Fairfield County||Mount Vernon|
|Lake||1840||Geauga and Cuyahoga Counties||Painesville|
|Lawrence||1815||Gallia and Scioto Counties||Ironton|
|Lorain||1822||Huron, Cuyahoga, and Medina Counties||Elyria|
|Lucas||1835||Wood, Sandusky, and Huron Counties||Toledo|
|Mahoning||1846||Columbiana and Trumbull Counties||Youngstown|
|Meigs||1819||Gallia and Athens Counties||Pomeroy|
|Monroe||1813||Belmont, Washington, and Guernsey Counties||Woodsfield|
|Montgomery||1803||Hamilton and Wayne Counties||Dayton|
|Morgan||1817||Washington, Guernsey, and Muskingum Counties||McConnelsville|
|Morrow||1848||Knox, Marion, Delaware, and Richland Counties||Mount Gilead|
|Muskingum||1803||Washington and Fairfield Counties||Zanesville|
|Noble||1851||Monroe, Washington, Morgan, and Guernsey Counties||Caldwell|
|Ottawa||1840||Erie, Sandusky, and Lucas Counties||Port Clinton|
|Perry||1818||Washington, Fairfield, and Muskingum Counties||New Lexington|
|Pickaway||1810||Ross, Fairfield, and Franklin Counties||Circleville|
|Pike||1815||Ross, Scioto, and Adams Counties||Waverly|
|Preble||1808||Montgomery and Butler Counties||Eaton|
|Ross||1798||Adams and Washington Counties||Chillicothe|
|Summit||1840||Medina, Portage, and Stark Counties||Akron|
|Trumbull||1800||Jefferson and Wayne Counties||Warren|
|Tuscarawas||1808||Muskingum County||New Philadelphia|
|Union||1820||Delaware, Franklin, Logan, and Madison Counties||Marysville|
|Van Wert||1820||Darke County||Van Wert|
|Vinton||1850||Athens, Gallia, Hocking, Jackson, and Ross Counties||McArthur|
|Washington||1788||One of the original counties||Marietta|
|Wayne||1808||From non-county area||Wooster|
|Wood||1820||Refactored from non-county territory||Bowling Green|
|Wyandot||1845||Marion, Crawford, and Hardin Counties||Upper Sandusky|
List of Old Former / Extinct Ohio Counties
Ohio contains some counties that no longer exist because they were discontinued, renamed or merged with another county. These are important for genealogy research purposes.
The below counties formerly within the area of the State of Ohio no longer exist:
Illinois County, Virginia
The Commonwealth of Virginia ceded Illinois County, and its charter claims to territory “northwestward of the river Ohio, to the new United States federal government in 1784.
The area later became theNorthwest Territoryby an Act of Congress in 1787.