| County | FIPS code | County seat | Est. | Origin | Etymology | Population(2024) | Area | Map |
| Alcona County | 001 | Harrisville | 1840 (boundaries declared)1869 (organized) | From unorganized territory; named Negwegon County until 1843 | Schoolcraft pseudo-Native American name | 10,624 | 1,791 sq mi(4,639 km2) | |
| Alger County | 003 | Munising | 1885 | From part of Schoolcraft County | Russell A. Alger, (1836-1907):Governor and national politician | 8,695 | 5,049 sq mi(13,077 km2) | |
| Allegan County | 005 | Allegan | 1831 (boundaries declared)1835 (organized) | From part of Barry County, and unorganized territory | Schoolcraft pseudo-Native American name | 122,429 | 1,833 sq mi(4,747 km2) | |
| Alpena County | 007 | Alpena | 1840 (boundaries declared)1857 (organized) | From part of Mackinac County, and unorganized territory Was named Anamickee County until 1843. | Schoolcraft pseudo-Native American name | 28,903 | 1,695 sq mi(4,390 km2) | |
| Antrim County | 009 | Bellaire | 1840 (boundaries declared)1863 (organized) | From part of Mackinac County; named Meegisee County until 1843 | County Antrim, now in Northern Ireland | 24,536 | 602 sq mi(1,559 km2) | |
| Arenac County | 011 | Standish | 1831 (boundaries established)1883 (organized) | From unorganized territory; annexed to Bay County in 1857, but reinstated in 1883 | Schoolcraft pseudo-Native American name | 15,087 | 681 sq mi(1,764 km2) | |
| Baraga County | 013 | L'Anse | 1875 | From part of Houghton County | Frederic Baraga (1797-1868): Catholic missionary and first bishop of Sault Ste. Marie | 8,169 | 1,069 sq mi(2,769 km2) | |
| Barry County | 015 | Hastings | 1829 (boundaries established)1839 (organized) | From unorganized territory | William T. Barry (1784-1835): Postmaster General in the Jackson Administration | 64,025 | 577 sq mi(1,494 km2) | |
| Bay County | 017 | Bay City | 1857 | From parts of Arenac, Midland, and Saginaw Counties | Saginaw Bay | 102,651 | 631 sq mi(1,634 km2) | |
| Benzie County | 019 | Beulah | 1863 | From part of Leelanau County | French name of Betsie River: (rivière aux) Bec-scies, the "(river of) sawbill ducks" | 18,520 | 860 sq mi(2,227 km2) | |
| Berrien County | 021 | St. Joseph | 1829 | From unorganized territory | John M. Berrien (1781-1856): Attorney General in the Jackson Administration | 152,703 | 1,581 sq mi(4,095 km2) | |
| Branch County | 023 | Coldwater | 1829 | From unorganized territory | John Branch (1782-1863): Secretary of the Navy in the Jackson Administration | 46,187 | 519 sq mi(1,344 km2) | |
| Calhoun County | 025 | Marshall | 1829 | From unorganized territory | John C. Calhoun (1782-1850): Vice President of the United States in the Jackson Administration | 133,785 | 718 sq mi(1,860 km2) | |
| Cass County | 027 | Cassopolis | 1829 | From unorganized territory | Lewis Cass (1782-1866): Secretary of War in the Jackson Administration | 51,550 | 508 sq mi(1,316 km2) | |
| Charlevoix County | 029 | Charlevoix | 1869 | From parts of Antrim, Emmet, and Otsego Counties | Pierre François Xavier de Charlevoix (1682-1761): Jesuit traveller and historian of New France | 26,105 | 1,391 sq mi(3,603 km2) | |
| Cheboygan County | 031 | Cheboygan | 1840 | From part of Mackinac County | Cheboygan River | 25,964 | 885 sq mi(2,292 km2) | |
| Chippewa County | 033 | Sault Ste. Marie | 1827 | From part of Mackinac County | Ojibwa Native American tribe, also known as the Chippewa | 36,253 | 2,698 sq mi(6,988 km2) | |
| Clare County | 035 | Harrison | 1840 | From part of Mackinac County, and unorganized territory; named Kaykakee County until 1843 | County Clare, Ireland | 31,405 | 575 sq mi(1,489 km2) | |
| Clinton County | 037 | St. Johns | 1831 | From unorganized territory | DeWitt Clinton (1769-1828): Governor of New York. | 80,050 | 575 sq mi(1,489 km2) | |
| Crawford County | 039 | Grayling | 1840 | From part of Mackinac County and unorganized territory. Was named Shawano County until 1843. | William Crawford, (1732-82), American Revolutionary War colonel western surveyor | 13,599 | 563 sq mi(1,458 km2) | |
| Delta County | 041 | Escanaba | 1843 | From part of Mackinac County and unorganized territory. | Greek letter delta, referring to the triangular shape of the original county, which included segments of Menominee, Dickinson, Iron and Marquette counties | 36,687 | 1,992 sq mi(5,159 km2) | |
| Dickinson County | 043 | Iron Mountain | 1891 | From parts of Iron County, Marquette County and Menominee County. | Donald M. Dickinson (1846-1917): Postmaster General in the Cleveland Administration | 25,995 | 777 sq mi(2,012 km2) | |
| Eaton County | 045 | Charlotte | 1829 | From unorganized territory. | John Eaton (1790-1856): Secretary of War in the Jackson Administration | 109,494 | 579 sq mi(1,500 km2) | |
| Emmet County | 047 | Petoskey | 1840 | From part of Mackinac County. Was named Tonegadana County until 1843. | Robert Emmet (1778-1803): Irish nationalist and rebel leader | 33,949 | 882 sq mi(2,284 km2) | |
| Genesee County | 049 | Flint | 1835 | From parts of Lapeer County, Saginaw County and Shiawassee County. | Seneca word, "je-nis-hi-yeh," meaning "beautiful valley": named after western New York valley from which many settlers came | 402,279 | 649 sq mi(1,681 km2) | |
| Gladwin County | 051 | Gladwin | 1831 | From unorganized territory. | Major Henry Gladwin, British commander of the fort at Detroit during the siege by Chief Pontiac in 1763-64. | 25,995 | 516 sq mi(1,336 km2) | |
| Gogebic County | 053 | Bessemer | 1887 | From part of Ontonagon County. | Probably from the Chippewa "bic" which most references interpret as "rock." | 14,217 | 1,476 sq mi(3,823 km2) | |
| Grand Traverse County | 055 | Traverse City | 1840 (boundaries declared)1851 (organized) | From part of Mackinac County; named Omeena County until 1851. | French grande traverse ("long crossing"), given first to Grand Traverse Bay by French voyageurs. | 96,625 | 601 sq mi(1,557 km2) | |
| Gratiot County | 057 | Ithaca | 1831 | From unorganized territory. | Captain Charles Gratiot (1788-1855), built Fort Gratiot at the present site of Port Huron | 41,372 | 572 sq mi(1,481 km2) | |
| Hillsdale County | 059 | Hillsdale | 1829 | From unorganized territory. | From its terrain, made up of hills and dales. | 45,590 | 607 sq mi(1,572 km2) | |
| Houghton County | 061 | Houghton | 1845 | From parts of Marquette County and Ontonagon County. | Douglass Houghton (1809-1845), first state geologist of Michigan, physician and surgeon, mayor of Detroit (1842-1843) | 38,041 | 1,502 sq mi(3,890 km2) | |
| Huron County | 063 | Bad Axe | 1840 | From part of Sanilac County. | Lake Huron, which the French named lac des Hurons after the Hurons. | 30,780 | 2,136 sq mi(5,532 km2) | |
| Ingham County | 065 | Mason | 1829 (boundaries declared)1838 (organized) | From parts of Shiawassee County, Washtenaw County and unorganized territory. | Samuel D. Ingham (1779-1860), U.S. Secretary of the Treasury in the Jackson Administration | 290,427 | 561 sq mi(1,453 km2) | |
| Ionia County | 067 | Ionia | 1831 | From part of Mackinac County and unorganized territory. | Province in ancient Greece | 66,250 | 580 sq mi(1,502 km2) | |
| Iosco County | 069 | Tawas City | 1840 | From unorganized territory. Was named Kanotin County until 1843. | Schoolcraft pseudo-Native American name | 25,361 | 1,891 sq mi(4,898 km2) | |
| Iron County | 071 | Crystal Falls | 1885 | From parts of Marquette County and Menominee County. | For the iron deposits and mines found in the county | 11,709 | 1,211 sq mi(3,136 km2) | |
| Isabella County | 073 | Mt. Pleasant | 1831 | From part of Mackinac County and unorganized territory. | Queen Isabella I (1451-1504) of Spain, under whose patronage Columbus undertook his voyages. | 65,072 | 578 sq mi(1,497 km2) | |
| Jackson County | 075 | Jackson | 1829 (boundaries declared)1832 (organised) | From part of Washtenaw County and unorganized territory. | Andrew Jackson (1767-1845), 7th President of the United States and President when Michigan was admitted to the Union | 160,233 | 724 sq mi(1,875 km2) | |
| Kalamazoo County | 077 | Kalamazoo | 1829 | From unorganized territory. | Named for the Kalamazoo River. See Etymology of Kalamazoo for a discussion of the river's name. | 264,780 | 580 sq mi(1,502 km2) | |
| Kalkaska County | 079 | Kalkaska | 1840 | From part of Mackinac County. Was named Wabassee County until 1843. | Schoolcraft pseudo-Native American name | 18,618 | 571 sq mi(1,479 km2) | |
| Kent County | 081 | Grand Rapids | 1831 | From part of Mackinac County and unorganized territory. | New York jurist James Kent, who represented the Michigan Territory in its dispute with Ohio over the Toledo Strip. | 673,002 | 872 sq mi(2,258 km2) | |
| Keweenaw County | 083 | Eagle River | 1861 | From part of Houghton County. | Ojibwe word gakiiwe-wewaning meaning "portage" | 2,161 | 5,966 sq mi(15,452 km2) | |
| Lake County | 085 | Baldwin | 1840 | From part of Mackinac County. Was named Aischum County until 1843. | Has several small lakes and lies near Lake Michigan | 13,005 | 575 sq mi(1,489 km2) | |
| Lapeer County | 087 | Lapeer | 1822 | From parts of Oakland County and St. Clair County. | An Americanization of the French la pierre, meaning "the rock" (flint) | 89,168 | 663 sq mi(1,717 km2) | |
| Leelanau County | 089 | Suttons Bay Township | 1840 | From part of Mackinac County. | Schoolcraft pseudo-Native American name | 22,871 | 2,532 sq mi(6,558 km2) | |
| Lenawee County | 091 | Adrian | 1822 | From part of Monroe County. | A Schoolcraft pseudo-Native American name for man, from either the Delaware leno or lenno or the Shawnee lenawai | 97,746 | 761 sq mi(1,971 km2) | |
| Livingston County | 093 | Howell | 1833 (boundaries declared)1836 (organized) | From parts of Shiawassee County and Washtenaw County. | Edward Livingston (1764-1836): second Secretary of State in the Andrew Jackson administration | 196,976 | 585 sq mi(1,515 km2) | |
| Luce County | 095 | Newberry | 1887 | From parts of Chippewa County and Mackinac County. | Named for Michigan Governor Cyrus G. Luce | 6,328 | 1,912 sq mi(4,952 km2) | |
| Mackinac County | 097 | St. Ignace | 1818 | From part of Wayne County. Was named Michilimackinac County until 1837. | Originally Michilimackinac, believed to be a French interpretation of the Native American name for Mackinac Island, meaning "big turtle" | 11,144 | 2,101 sq mi(5,442 km2) | |
