Bay County is a county in the U.S. state of Michigan. As of the 2010 census, the population was 107,771. The county seat is Bay City.
According to the U.S. Census Bureau, the county has a total area of 631 square miles (1,630 km), of which 442 square miles (1,140 km) is land and 188 square miles (490 km) (30%) is water. It is the fifth-smallest county in Michigan by land area.
The Saginaw River flows through Bay City while the Kawkawlin River drains much of the central portion of the county. The Pinconning River and Saganing Creek drain the northern portion. The Saginaw Bay of Lake Huron lies to the east, giving the county its name.
The 2010 United States Census indicates Bay County had a 2010 population of 107,771. This is a decrease of -2,386 people from the 2000 United States Census. Overall, the county had a -2.2% growth rate during this ten-year period. In 2010 there were 44,603 households and 29,116 families in the county. The population density was 243.7 per square mile (94.1 square kilometers). There were 48,220 housing units at an average density of 109.0 per square mile (42.1 square kilometers). The racial and ethnic makeup of the county was 91.2% White, 1.5% Black or African American, 0.4% Native American, 0.5% Asian, 4.7% Hispanic or Latino, 0.1% from other races, and 1.6% from two or more races.
There were 44,603 households out of which 28.5% had children under the age of 18 living with them, 48.6% were husband and wife families, 11.8% had a female householder with no husband present, 34.7% were non-families, and 29.3% were made up of individuals. The average household size was 2.38 and the average family size was 2.92.
In the county, the population was spread out with 22.2% under age of 18, 8.5% from 18 to 24, 23.6% from 25 to 44, 29.5% from 45 to 64, and 16.2% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 95.9 males. For every 100 females age 18 and over, there were 93 males.
The 2010 American Community Survey 1-year estimate indicates the median income for a household in the county was $45,451 and the median income for a family was $52,784. Males had a median income of $31,035 versus $18,294 for females. The per capita income for the county was $22,378. About 11.2% of families and 16.2% of the population were below the poverty line, including 23.7% of those under the age 18 and 7.0% of those age 65 or over.
The Roman Catholic Diocese of Saginaw is the controlling regional body for the Catholic Church.