The county was formed April 1, 1840, from Mackinac County. It was first named Tonedagana County and renamed Emmet County on March 8, 1843. Emmet County remained attached to Mackinac County for administrative purposes until county government was organized in 1853. The county was named for the Irish patriot Robert Emmet, who was hanged as a traitor to the British government at the age of 23. Sixteen counties were renamed in 1843 and five were given names of Irish origin, supposedly in deference to the increasing presence of settlers in Michigan with an Irish background. See, List of Michigan county name etymologies.
Emmet County is located at the top of the mitten-shaped Lower Peninsula of Michigan, with Lake Michigan to the west, the Straits of Mackinac to the north, Cheboygan County to the east, and Charlevoix County to the south.
As of the census of 2000, there were 31,437 people, 12,577 households, and 8,527 families residing in the county. The population density was 67 people per square mile (26/km²). There were 18,554 housing units at an average density of 40 per square mile (15/km²). The racial makeup of the county was 94.33% White, 0.47% Black or African American, 3.11% Native American, 0.43% Asian, 0.03% Pacific Islander, 0.16% from other races, and 1.47% from two or more races. 0.91% of the population were Hispanic or Latino of any race. 23.6% were of German, 11.4% English, 11.3% Irish, 9.0% Polish and 8.4% American ancestry according to Census 2000. 96.9% spoke English and 1.1% Spanish as their first language.
There were 12,577 households out of which 31.70% had children under the age of 18 living with them, 55.90% were married couples living together, 8.50% had a female householder with no husband present, and 32.20% were non-families. 26.90% of all households were made up of individuals and 10.00% had someone living alone who was 65 years of age or older. The average household size was 2.44 and the average family size was 2.97.
In the county the population was spread out with 25.30% under the age of 18, 7.10% from 18 to 24, 28.10% from 25 to 44, 25.20% from 45 to 64, and 14.30% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 96.80 males. For every 100 females age 18 and over, there were 93.70 males.
The median income for a household in the county was $40,222, and the median income for a family was $48,140. Males had a median income of $33,385 versus $24,173 for females. The per capita income for the county was $21,070. About 4.50% of families and 7.40% of the population were below the poverty line, including 7.30% of those under age 18 and 7.80% of those age 65 or over.