1850 Counties of Ohio
| in area | Courts held at | Pop in 1850 | ||
| Adams Co, OH | southern part, on Ohio river | 550 sq miles | Adamsvile & West Union | 18,853 |
| Allen Co, OH | northwest part, water by Auglaize, St Mary's & Miami rivers | 554 sq miles | Lima | 12,109 |
| Ashland Co, OH | northern part | (blank) | Ashland | 23,811 |
| Ashtabula Co, OH | northeast part on Lake Erie, water by Grand & Ashtabula river | 700 sq miles | Jefferson | 28,766 |
| Athens Co, OH | southeast part, next to Ohio river & crossed by Hockkocking river | 900 sq miles | Athens | 18,215 |
| Auglaize Co, OH | western part | (blank) | Wapaukonetta | 11,344 |
| Belmont Co, OH | in east part, on west died of Ohio river | 500 sq miles | St Clairsville | 34,600 |
| Brown Co, OH | south boundary, on north side of Ohio river | 470 sq miles | Georgetown | 27,332 |
| Butler Co, OH | southwest part, crossed by Miami river & the Miami canal | 480 sq miles | Hamilton | 30,789 |
| Carroll Co, OH | eastern part | 400 | Carrollton | 17,685 |
| Champaign Co, OH | western part, crossed by Mud river | 450 | Urbana | 19,762 |
| Clermont Co, OH | southern boundary, on north side of Ohio river | 450 | Batavia | 30,455 |
| Clinton Co, OH | southwest corner, drained by tributaries of Little Miami river | 400 | Wilmington | 18,838 |
| Columbiana Co, OH | east boundary, Ohio river on southeast | 750 | New Lisbon | 33,621 |
| Coshocton Co, OH | near central part | 562 | Coshocton | 25,674 |
| Crawford Co, OH | north part, drained by Sandusky river | 590 | Bueyrus | 18,177 |
| Cuyahoga Co, OH | northern boundary on Lake Erie, crossed by Cuyahoga river | 475 | Cleveland | 48,099 |
| Darke Co, OH | western boundary | 714 | Greenville | 20,274 |
| Defiance Co, OH | west boundary, crossed by Maumee river | blank | Defiance | 6,966 |
| Delaware Co, OH | central part, water by Scioto & Whetstone rivers | 610 | Delaware | 21,817 |