Plymouth is a city in Cerro Gordo County, Iowa, United States, along the Shell Rock River. The population was 375 at the time of the 2020 census. It is part of the Mason City Micropolitan Statistical Area. Geography Plymouth is located at (43.245346, -93.122575). According to the United States Census Bureau, the city has a total area of , all land. Demographics 2010 census As of the census of 2010, there were 382 people, 164 households, and 111 families residing in the city. The population density was . There were 180 housing units at an average density of . The racial makeup of the city was 97.4% White, 0.5% African American, 0.3% Native American, 0.3% Asian, 0.3% Pacific Islander, and 1.3% from two or more races. Hispanic or Latino of any race were 2.4% of the population. There were 164 households, of which 25.0% had children under the age of 18 living with them, 57.9% were married couples living together, 6.1% had a female householder with no husband present, 3.7% had a male householder with no wife present, and 32.3% were non-families. 27.4% of all households were made up of individuals, and 7.3% had someone living alone who was 65 years of age or older. The average household size was 2.33 and the average family size was 2.79. The median age in the city was 45.4 years. 18.8% of residents were under the age of 18; 9.8% were between the ages of 18 and 24; 20.7% were from 25 to 44; 36.5% were from 45 to 64; and 14.4% were 65 years of age or older. The gender makeup of the city was 52.4% male and 47.6% female. 2000 census As of the census of 2000, there were 429 people, 164 households, and 120 families residing in the city. The population density was . There were 171 housing units at an average density of . The racial makeup of the city was 98.83% White, 0.70% Native American, and 0.47% from two or more races. Hispanic or Latino of any race were 1.17% of the population. There were 164 households, out of which 35.4% had children under the age of 18 living with them, 63.4% were married couples living together, 7.9% had a female householder with no husband present, and 26.8% were non-families. 22.0% of all households were made up of individuals, and 11.6% had someone living alone who was 65