Marysville is a city in St. Clair County of the U.S. state of Michigan. The population was 9,684 at the 2000 census.
As of the census of 2000, there were 9,684 people, 4,025 households, and 2,741 families residing in the city. The population density was 1,395.6 per square mile (538.8/km²). There were 4,180 housing units at an average density of 602.4 per square mile (232.6/km²). The racial makeup of the city was 98.18% White, 0.18% African American, 0.30% Native American, 0.43%Asian, 0.01% Pacific Islander, 0.33% from other races, and 0.57% from two or more races. Hispanic or Latino of any race were 1.16% of the population.
There were 4,025 households out of which 30.8% had children under the age of 18 living with them, 57.4% were married couples living together, 8.0% had a female householder with no husband present, and 31.9% were non-families. 28.5% of all households were made up of individuals and 14.3% had someone living alone who was 65 years of age or older. The average household size was 2.40 and the average family size was 2.96.