St. Clair County, Michigan
County
Fort Gratiot Light
Seal
Location within the U.S. state of Michigan
Coordinates: 42°56′N 82°40′W / 42.93°N 82.67°W / 42.93; -82.67
Country	United States
State	Michigan
Founded	March 28, 1820 (created) 1821 (organized)[1][2]
Named after	St. Clare of Assisi
Seat	Port Huron
Largest city	Port Huron
Area
• Total	837 sq mi (2,170 km2)
• Land	721 sq mi (1,870 km2)
• Water	115 sq mi (300 km2)  14%
Population  (2020)
• Total	160,383
• Estimate  (2024)	160,308
• Density	190/sq mi (73/km2)
Time zone	UTC−5 (Eastern)
• Summer (DST)	UTC−4 (EDT)
Area code	810
Congressional district	9th
Website	www.stclaircounty.org

St. Clair County is a county located in the U.S. state of Michigan and bordering the west bank of the St. Clair River. As of the 2020 census, the population was 160,383.^[3] It is the 13th-most populous county in the state. The county seat is Port Huron, located at the north end of the St. Clair River at Lake Huron.^[1][4] The county was created September 10, 1820, and its government was organized in 1821.^[1] It is located northeast of Detroit. It is considered by the State of Michigan to be a part of The Thumb, a peninsula that is surrounded by Lake Huron in the east-central area of the state.^[5] This area is sometimes dubbed the Blue Water Area.^[6]

French explorer René-Robert Cavelier, Sieur de La Salle led an expedition to this area on August 12, 1679. They named the lake as Lac Sainte-Claire, because it was the feast day of Saint Clare of Assisi, whom they venerated.^[1][7] English mapmakers adopted the French name, identifying the lake feature as Saint Clare on maps dated as early as 1710. By the Mitchell Map of 1755, the spelling was given as St. Clair, which later became the current version in 1924.^[8] Located along the western shores of Lake St. Clair and the St. Clair River, the county was named for them by European-American settlers.

The name is sometimes mistakenly attributed to honoring Arthur St. Clair, an American Revolutionary War general and governor of the Northwest Territory, but it was established long before he was considered a notable figure.^[9] The earlier spelling of the lake's name may have been conflated with English practice and the name of the general, as several political jurisdictions near the lake and the river, such as St. Clair County, St. Clair Township, and the cities of St. Clair and St. Clair Shores, share this spelling (see List of Michigan county name etymologies).

The name has sometimes been mistakenly attributed to honoring Patrick Sinclair, a British officer who purchased land on the St. Clair River at the mouth of the Pine River. In 1764, he built Fort Sinclair there, which was in use for nearly 20 years before being abandoned.^[10] As noted, the name was established before he was active in the area.

According to the U.S. Census Bureau, the county has a total area of 837 square miles (2,170 km²), of which 721 square miles (1,870 km²) is land and 115 square miles (300 km²) (14%) is water.^[11] St. Clair County is one of five counties that form the peninsula, known as the Thumb, that projects into Lake Huron. St. Clair County is closely connected in terms of economy with its neighbors, Metro Detroit and Sanilac County in Michigan, and Lambton County across the river in Ontario, Canada. Saint Clair County is the principal county in The Blue Water Area, a sub-region of the Thumb.

• Sanilac (north)
• Lapeer (west)
• Macomb (south)
• Lambton, Ontario (east)

• I-69 enters the county from the west, coming from Lansing and Flint, terminating at the approach to the Blue Water Bridge in Port Huron. (Once fully completed, the mainline of I-69 will span from Brownsville, Texas to Port Huron, Michigan.)
• I-94 enters St. Clair County from the southwest, having traversed the entire Metro Detroit region, and terminates at the approach to the Blue Water Bridge in Port Huron. On the Canadian side of the border, in Sarnia, Ontario, the route heads easterly, designated as Highway 402.
• BL I-69
• BL I-94
• M-19
• M-25 follows the Lake Huron–Saginaw Bay shoreline, beginning in Bay City and ending at a junction with |I-94/|I-69, and BL I-94/BL I-69 on the north side of Port Huron.
• M-29
• M-136
• M-154 serves Harsens Island, in Lake St. Clair.

Historical population

Census	Pop.	Note	%±
1830	1,114		—
1840	4,606		313.5%
1850	10,420		126.2%
1860	26,604		155.3%
1870	36,661		37.8%
1880	46,197		26.0%
1890	52,105		12.8%
1900	55,228		6.0%
1910	52,341		−5.2%
1920	58,009		10.8%
1930	67,563		16.5%
1940	76,222		12.8%
1950	91,599		20.2%
1960	107,201		17.0%
1970	120,175		12.1%
1980	138,802		15.5%
1990	145,607		4.9%
2000	164,235		12.8%
2010	163,040		−0.7%
2020	160,383		−1.6%
2024 (est.)	160,308	[12]	0.0%
U.S. Decennial Census[13] 1790–1960[14] 1900–1990[15] 1990–2000[16] 2010–2019[3]

As of the 2020 census, the county had a population of 160,383 and a median age of 44.5 years. 20.5% of residents were under the age of 18 and 19.6% of residents were 65 years of age or older. For every 100 females there were 99.2 males, and for every 100 females age 18 and over there were 97.6 males.^[17]

The racial makeup of the county was 90.1% White, 2.5% Black or African American, 0.4% American Indian and Alaska Native, 0.5% Asian, <0.1% Native Hawaiian and Pacific Islander, 0.9% from some other race, and 5.6% from two or more races. Hispanic or Latino residents of any race comprised 3.4% of the population.^[18]

60.5% of residents lived in urban areas, while 39.5% lived in rural areas.^[19]

There were 65,724 households in the county, of which 26.4% had children under the age of 18 living in them. Of all households, 48.5% were married-couple households, 19.0% were households with a male householder and no spouse or partner present, and 24.5% were households with a female householder and no spouse or partner present. About 28.3% of all households were made up of individuals and 13.0% had someone living alone who was 65 years of age or older.^[17]

There were 72,092 housing units, of which 8.8% were vacant. Among occupied housing units, 77.0% were owner-occupied and 23.0% were renter-occupied. The homeowner vacancy rate was 1.2% and the rental vacancy rate was 6.5%.^[17]

The 2010 United States census indicates St. Clair County had a 2010 population of 163,040, a decrease of 1,195 people from the 2000 United States census and an overall growth rate of −0.7% during that decade. In 2010 there were 63,841 households and 44,238 families in the county. The population density was 226.1 per square mile (87.3 per square kilometer). There were 71,822 housing units at an average density of 99.6 per square mile (38.5 per square kilometer).^[20]

93.9% were White, 2.4% Black or African American, 0.5% Asian, 0.4% Native American, 0.7% of some other race, and 2.0% of two or more races. 2.9% were Hispanic or Latino (of any race). 25.9% identified as of German, 10.2% Polish, 9.3% Irish, 8.5% English, 6.5% French, 6.5% American, and 5.1% Italian ancestry.^[20]

Of the 63,841 households, 31.3% had children under the age of 18 living with them, 52.9% were opposite-sex families, 11.4% had a female householder with no husband present, 30.7% were non-families, and 25.5% were made up of individuals. The average household size was 2.52 and the average family size was 3.01.^[20]

In the county, 23.7% of the population was under the age of 18, 8.0% was from 18 to 24, 23.8% from 25 to 44, 30.1% from 45 to 64, and 14.5% was 65 years of age or older. The median age was 41 years. For every 100 females, there were 98.1 males. For every 100 females age 18 and over, there were 95.7 males.^[20]

The 2010 American Community Survey 1-year estimate indicates the median income for a household in the county was $44,369 and the median income for a family was $53,207. Males had a median income of $30,056 versus $16,771 for females. The per capita income for the county was $22,390. About 10.4% of families and 15.4% of the population were below the poverty line, including 22.7% of those under the age of 18 and 6.8% of those age 65 or over.^[20]

The county government operates the jail, maintains rural roads, operates the major local courts, keeps files of deeds and mortgages, maintains vital records, administers public health regulations, and participates with the state in the provision of welfare and other social services. The county board of commissioners controls the budget but has only limited authority to make laws or ordinances. In Michigan, most local government functions — police and fire, building and zoning, tax assessment, street maintenance, etc. — are the responsibility of individual cities and townships.

• Prosecuting attorney: Michael D. Wendling^[21]
• Sheriff: Mat King^[22]
• County clerk/register of deeds: Angie Waters^[23][24][25]
• County treasurer: Kelly Roberts-Burnett^[26]
• Drain commissioner: Robert Wiley^[27]
• County commissioner, district 1: Steven Simasko^[28]
• County commissioner, district 2: Jorja Baldwin
• County commissioner, district 3: Lisa Beedon
• County commissioner, district 4: Joi Torello
• County commissioner, district 5: Jeffrey L. Bohm
• County commissioner, district 6: David Rushing
• County commissioner, district 7: Dave Vandenbossche
• 31st Circuit Court: Cynthia Lane, Michael West, Daniel Damman^[29]
• 72nd District Court: Michael Hulewicz; John Monaghan; Mona Armstrong^[30]
• Probate Court: Jennifer Deegan; John Tomlinson^[31]

(information as of February 2023)

• Algonac State Park

St. Clair County is home to five county parks: Columbus County Park, Fort Gratiot County Park, Fort Gratiot Light station, Goodells County Park, and Woodsong County Park. St. Clair County also operates the Wadhams to Avoca Trail and works with local units of government to develop the Bridge to Bay Trail.^[34]

• Algonac
• Marine City
• Marysville
• Memphis (partial)
• Port Huron (county seat)
• Richmond (partial)
• St. Clair
• Yale

• Capac
• Emmett

• China Charter Township
• East China Charter Township
• Fort Gratiot Charter Township
• Port Huron Charter Township

• Lakeport
• Pearl Beach
• Ruby

• List of Michigan State Historic Sites in St. Clair County
• National Register of Historic Places listings in St. Clair County, Michigan
• Blue Water River Walk

• Fuller, George Newman (2005) [1926?]. "Indians and Explorations". Local history and personal sketches of St. Clair and Shiawassee counties. Ann Arbor, Mich.: University of Michigan Library. pp. 17–27. Retrieved November 23, 2007.
• Jenks, William Lee (2005) [1912]. "Origin of Name". St. Clair County, Michigan, its history and its people. Ann Arbor, Mich.: University of Michigan Library. pp. 20–24. Retrieved November 23, 2007.

• St. Clair County
• Info and photos of historic bridges in St. Clair County
• "Bibliography on St. Clair County". Clarke Historical Library, Central Michigan University. Retrieved January 29, 2013.

42°56′N 82°40′W / 42.93°N 82.67°W / 42.93; -82.67