1850 Counties of Michigan
| County | Description | Area in sq miles | Courts held at | Pop in 1850 |
| Allegan | south west side on Lake Michigan near Kalamazoo, Black & Rabbit rivers | 700 | Allegan | 5,125 |
| Barry | in southwest part, drained by Thornapple river | 576 | Hastings | 5,072 |
| Berrien | SW corner, Lake MI on west, water by St Joseph & Gallon rivers | 576 | Berrien Springs | 11,471 |
| Branch | south boundary, drained by St Joseph river | 528 | Branch Court House | 18,472 |
| Calhoun | southern part, drained by Kalamazoo & St Joseph's rivers | 720 | Marshall | 13,162 |
| Cass | south boundary | 528 | Cassopolis | 10,907 |
| Cheboygan | north part of peninsula, straits of Mackinaw on the north | 300 | Duncan | not listed |
| Chippeway | northern boundary | 7200 | Sault de St Marie | 898 |
| Clinton | southern part, water by Grand Maple & Lookinglass rivers | 576 | De Witt | 5,102 |
| Eaton | near central part | 576 | Eaton | 7,058 |
| Genesee | eastern part, crossed by Flint river | 504 | Flint | 11,632 |
| Gladwin | eastern part, crossed by Tittibawasee river | blank | blank | blank |
| Gratiot | central part | 576 | blank | not listed |
| Hillsdale | southern boundary | 576 | Hillsdale | 16,159 |
| Ingham | southern part | 560 | Lansing | 8,631 |
| Ionia | western part, crossed by Grand river | 576 | Ionia | 7,597 |
| Houghton | north western part on Lake Superior | not listed | Eagle Harbor | 708 |
| Huron | eastern boundary, Lake Michigan on east & Suganaw bay on north | blank | blank | 210 |
| Isabella | central part, crossed by Chippewa river | 579 | blank | not listed |
| Jackson | southern part | 720 | Jackson | 19,431 |
| Kalamazoo | southwest part | 576 | Kalamazoo | 13,179 |
| Kent | western part, crossed by Grand river | 576 | Kent or Grand Rapids | 12,016 |
| Lapeer | eastern part | 828 | Lapeer | 7,029 |
| Lenawee | south boundary | 735 | Adrian | 24,572 |
| Livingston | toward east part | 576 | Howell | 13,485 |
| Macomb | east part on Lake St Clair | 485 | Mount Clemens | 15,530 |
| Manistee | western boundary on Lake Michigan, crossed by Manistee river | blank | Manistee | 65 |
| Marquette | northwest part of the northern peninsula on Lake Superior | blank | blank | 136 |
| Michilimacknac | on the north peninsula, straits of Mackinaw on the south | blank | Mackinaw | 3,598 |
| Midland | east part on Saginaw bay, crossed by Titibawassee river | blank | Midland | 95 |
| Monroe | southeast corner on Lake Erie | 540 | Monroe | 14,698 |
| Montcalm | toward western part | blank | Montcalm | 891 |
| Oakland | eastern part | 900 | Pontiac | 31,270 |
| Oceana | west boundary, w Lake Michigan on west | blank | blank | 300 |
| Ottawa | western boundary, Lake Michigan on west, crossed by Gran river | blank | Grand Haven | 5,587 |
| Saginaw | northeastern part, crossed by Shiawassee, Saginaw, Flint & Tittibawassee rivers | blank | Saginaw | 2,609 |
| St Clair | on east boundary, Lake Huron & St Clair river on east, Lake St Clair on south | 930 | St Clair | 10,420 |
| St Joseph | south boundary, crossed by St Joseph river | 528 | Centreville | 12,705 |
| Sanilac | on east boundary, Lake Huron on east | 730 | Sanilac Mills | 2,112 |
| Shiawassee | central part, crossed by Shiawassee river | 544 | Corunna | 5,230 |
| Van Buren | on west boundary, Lake Michigan on west | 633 | Paw-Paw | 5,800 |
| Washtenaw | in southern part | 720 | Ann Arbor | 28,568 |
| Wayne | on southeasterly boundary, St Clair lake & St Clair river on east | 600 | Detroit | 32,756 |