2010 census

As of the census^[11] of 2010, there were 689 people, 302 households, and 196 families residing in the city. The population density was 177.6 inhabitants per square mile (68.6/km²). There were 348 housing units at an average density of 89.7 per square mile (34.6/km²). The racial makeup of the city was 98.7% White, 0.1% African American, 0.4% Asian, 0.1% from other races, and 0.6% from two or more races. Hispanic or Latino of any race were 0.6% of the population.

There were 302 households, of which 27.5% had children under the age of 18 living with them, 56.0% were married couples living together, 6.3% had a female householder with no husband present, 2.6% had a male householder with no wife present, and 35.1% were non-families. 29.8% of all households were made up of individuals, and 11.6% had someone living alone who was 65 years of age or older. The average household size was 2.28 and the average family size was 2.84.

The median age in the city was 50 years. 21.8% of residents were under the age of 18; 3.6% were between the ages of 18 and 24; 13.2% were from 25 to 44; 42% were from 45 to 64; and 19.4% were 65 years of age or older. The gender makeup of the city was 47.2% male and 52.8% female.

2000 census

As of the census^[3] of 2000, there were 602 people, 254 households, and 178 families residing in the city. The population density was 152.8 inhabitants per square mile (59.0/km²). There were 290 housing units at an average density of 73.6 per square mile (28.4/km²). The racial makeup of the city was 98.34% White, 0.33% African American, 0.17% Asian, and 1.16% from two or more races. Hispanic or Latino of any race were 0.17% of the population.

There were 254 households, out of which 29.5% had children under the age of 18 living with them, 61.8% were married couples living together, 5.9% had a female householder with no husband present, and 29.9% were non-families. 23.6% of all households were made up of individuals, and 7.1% had someone living alone who was 65 years of age or older. The average household size was 2.37 and the average family size was 2.83.

In the city, the population was spread out, with 22.4% under the age of 18, 3.3% from 18 to 24, 26.1% from 25 to 44, 35.4% from 45 to 64, and 12.8% who were 65 years of age or older. The median age was 44 years. For every 100 females, there were 96.1 males. For every 100 females age 18 and over, there were 93.8 males.

The median income for a household in the city was $66,250, and the median income for a family was $77,633. Males had a median income of $51,705 versus $37,232 for females. The per capita income for the city was $32,383. About 3.1% of families and 2.8% of the population were below the poverty line, including 2.0% of those under age 18 and 5.4% of those age 65 or over.

Marine on St. Croix Historic District

A 450-acre (180 ha) historic district in Marine on St. Croix was listed on the National Register of Historic Places in 1974 for having state-level significance in the themes of architecture, commerce, exploration/settlement, and industry.^[14] It was nominated as the birthplace of Minnesota's lumber industry and for its representation of two separate but interdependent waves of immigration that created the town.^[15]

The district encompasses three distinct areas: the original business district bounded by Oak, 5th, and Mill Streets; the residential area of the Yankee business owners on the bluffs to the north, now bisected by Highway 95; and the residential areas of the Swedish working class, initially on the low areas to the north and south of the village center, and later on the bluff to the west. 60 buildings and three sites of ruins were identified as the contributing properties to the historic district in 1974.^[15]