According to the United States Census Bureau, the town has a total area of, of which, of it is land and is water. Monmouth is drained by Jug Stream, Jock Stream, Mud Mills Stream and Wilson Stream, Monmouth has access to Lakes Cobbosseecontee, Annabessacook, and Cochnewagen. The town is crossed by U.S. Route 202 and state routes 126, 132 and 135.
As of the census of 2010, there were 4,104 people, 1,577 households, and 1,174 families living in the town. The population density was. There were 2,021 housing units at an average density of. The racial makeup of the town was 97.9% White, 0.3% African American, 0.2% Native American, 0.1% Asian, 0.1% from other races, and 1.5% from two or more races. Hispanic or Latino of any race were 1.2% of the population. There were 1,577 households of which 34.3% had children under the age of 18 living with them, 59.8% were married couplesliving together, 10.1% had a female householder with no husband present, 4.6% had a male householder with no wife present, and 25.6% were non-families. 17.8% 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 2.59 and the average family size was 2.93. The median age in the town was 42 years. 23.2% of residents were under the age of 18; 7% were between the ages of 18 and 24; 24.4% were from 25 to 44; 33.7% were from 45 to 64; and 11.7% were 65 years of age or older. The gender makeup of the town was 48.6% male and 51.4% female.
2000 census
As of the census of 2000, there were 3,785 people, 1,435 households, and 1,077 families living in the town. The population density was 111.0 people per square mile. There were 1,801 housing units at an average density of 52.8 per square mile. The racial makeup of the town was 100.00% White, 0.20% African American, 0.42% Native American, 0.16% Asian, 0.03% from other races, and 0.58% from two or more races. Hispanic or Latino of any race were 0.69% of the population. There were 1,435 households out of which 39.0% had children under the age of 18 living with them, 61.0% were married couples living together, 10.0% had a female householder with no husband present, and 24.9% were non-families. 20.0% of all households were made up of individuals and 7.9% had someone living alone who was 65 years of age or older. The average household size was 2.63 and the average family size was 3.00. In the town, the population was spread out with 27.6% under the age of 18, 6.2% from 18 to 24, 31.7% from 25 to 44, 24.4% from 45 to 64, and 10.0% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 94.5 males. For every 100 females age 18 and over, there were 92.1 males. The median income for a household in the town was $43,906, and the median income for a family was $47,616. Males had a median income of $32,034 versus $22,885 for females. The per capita income for the town was $17,551. About 9.6% of families and 9.2% of the population were below the poverty line, including 11.5% of those under age 18 and 17.0% of those age 65 or over.
Divisions
North Monmouth
South Monmouth
East Monmouth
Monmouth Center
Points of interest
Cumston Hall, location of the Theater at Monmouth. Cumston Hall was donated in 1900.