2020 census

The 2020 United States census counted 948 people, 336 households, and 240 families in Garden Plain.^[8][9] The population density was 908.0 per square mile (350.6/km²). There were 349 housing units at an average density of 334.3 per square mile (129.1/km²).^[9][10] The racial makeup was 92.51% (877) white or European American (91.03% non-Hispanic white), 0.11% (1) black or African-American, 0.11% (1) Native American or Alaska Native, 0.42% (4) Asian, 0.0% (0) Pacific Islander or Native Hawaiian, 1.16% (11) from other races, and 5.7% (54) from two or more races.^[11] Hispanic or Latino of any race was 3.38% (32) of the population.^[12]

Of the 336 households, 38.7% had children under the age of 18; 60.4% were married couples living together; 22.6% had a female householder with no spouse or partner present. 25.6% of households consisted of individuals and 15.2% had someone living alone who was 65 years of age or older.^[9] The average household size was 3.2 and the average family size was 3.8.^[13] The percent of those with a bachelor’s degree or higher was estimated to be 24.1% of the population.^[14]

27.8% of the population was under the age of 18, 7.4% from 18 to 24, 23.8% from 25 to 44, 25.3% from 45 to 64, and 15.6% who were 65 years of age or older. The median age was 37.0 years. For every 100 females, there were 110.2 males.^[9] For every 100 females ages 18 and older, there were 113.1 males.^[9]

The 2016-2020 5-year American Community Survey estimates show that the median household income was $80,833 (with a margin of error of +/- $21,824) and the median family income was $95,208 (+/- $28,540).^[15] Males had a median income of $51,563 (+/- $24,700) versus $17,399 (+/- $11,604) for females. The median income for those above 16 years old was $33,125 (+/- $10,530).^[16] Approximately, 20.4% of families and 19.8% of the population were below the poverty line, including 28.6% of those under the age of 18 and 7.7% of those ages 65 or over.^[17][18]

2010 census

As of the census^[19] of 2010, there were 849 people, 308 households, and 221 families residing in the city. The population density was 1,415.0 inhabitants per square mile (546.3/km²). There were 320 housing units at an average density of 533.3 per square mile (205.9/km²). The racial makeup of the city was 97.8% White, 0.4% African American, 0.2% Native American, 0.1% Asian, 0.2% from other races, and 1.3% from two or more races. Hispanic or Latino of any race were 0.6% of the population.

There were 308 households, of which 43.2% had children under the age of 18 living with them, 58.4% were married couples living together, 8.8% had a female householder with no husband present, 4.5% had a male householder with no wife present, and 28.2% were non-families. 26.9% of all households were made up of individuals, and 15.3% had someone living alone who was 65 years of age or older. The average household size was 2.76 and the average family size was 3.40.

The median age in the city was 34.5 years. 33.1% of residents were under the age of 18; 6.8% were between the ages of 18 and 24; 24.9% were from 25 to 44; 22.5% were from 45 to 64; and 12.7% were 65 years of age or older. The gender makeup of the city was 49.7% male and 50.3% female.

2000 census

As of the census^[20] of 2000, there were 797 people, 286 households, and 201 families residing in the city. The population density was 1,474.8 inhabitants per square mile (569.4/km²). There were 292 housing units at an average density of 540.3 per square mile (208.6/km²). The racial makeup of the city was 97.37% White, 0.38% African American, 0.63% Native American, 0.13% Asian, 0.63% from other races, and 0.88% from two or more races. Hispanic or Latino of any race were 1.38% of the population.

There were 286 households, out of which 39.9% had children under the age of 18 living with them, 60.8% were married couples living together, 7.7% had a female householder with no husband present, and 29.4% were non-families. 27.3% of all households were made up of individuals, and 15.4% had someone living alone who was 65 years of age or older. The average household size was 2.79 and the average family size was 3.47.

In the city, the population was spread out, with 34.5% under the age of 18, 5.5% from 18 to 24, 26.9% from 25 to 44, 19.1% from 45 to 64, and 14.1% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 102.8 males. For every 100 females age 18 and over, there were 97.7 males.

As of 2000 the median income for a household in the city was $48,068, and the median income for a family was $56,375. Males had a median income of $40,750 versus $25,577 for females. The per capita income for the city was $22,946. About 2.8% of families and 4.0% of the population were below the poverty line, including 3.0% of those under age 18 and 6.7% of those age 65 or over.