[4] Macomb County contains 27 cities, townships and villages, including three of the ten most-populous municipalities in Michigan.

The Ojibwe lived in the area for centuries before European contact and were preceded by other cultures of ancient indigenous peoples.

In addition to the original French and English settlers, later immigrants included Germans, Belgians, and others from Europe.

In the 19th century, the county received many European-American migrants from New York and New England, who were attracted to the area for land and booming jobs in the lumber and other resource industries.

The county was named in honor of Detroit-born Alexander Macomb, Jr., a highly decorated veteran of the War of 1812 and hero of the Battle of Plattsburg.

As population increased in the area, the state legislature removed territory in 1819 and 1820 to form the counties of Oakland, Lapeer, Genesee, and St.

European ethnic groups that have settled in Macomb County since the late 20th century include Bosnians, Albanians and Macedonians.

[18] Of Michigan's five largest counties, Macomb experienced the most population growth (102.5%) in the post-World War II years of accelerating suburban development, between 1950 and 1960.

[19] 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.

In Michigan, most local government functions — police and fire, building and zoning, tax assessment, street maintenance, etc.

Macomb County has historically shown Republican tendencies in statewide elections, while tending to favor Democratic candidates at the federal and local level.

[21] Since the 2010s, Macomb County has shifted towards the Republicans, and after the 2020 elections the party gained control of the Board of Commissioners for the first time as well as four of the five countywide offices.

Macomb's large cohort of middle-class,[23] socially conservative White voters gave it one of the nation's most prominent concentrations of "Reagan Democrats".

[28] The more populated communities south of M-59 (Warren, Sterling Heights, Clinton Charter Township), closer to Detroit city proper are friendlier to Democrats.

[29][30] The communities north of M-59 further removed from Detroit are more strongly Republican, all backing Trump in 2016 and 2020 and Bill Schuette in 2018.