Byrnes Mill is a city in Jefferson County, Missouri, United States. The population was 2,781 at the 2010 census.
Byrnes Mill is located at 38°26′7″N 90°34′26″W / 38.43528°N 90.57389°W / 38.43528; -90.57389 (38.435197, -90.573838).
According to the United States Census Bureau, the city has a total area of 5.26 square miles (13.62 km), of which 5.14 square miles (13.31 km) is land and 0.12 square miles (0.31 km) is water.
The city is located on the Big River, and has the ruins of an old mill and dam.
As of the census of 2010, there were 2,781 people, 1,038 households, and 782 families residing in the city. The population density was 541.1 inhabitants per square mile (208.9/km). There were 1,121 housing units at an average density of 218.1 per square mile (84.2/km). The racial makeup of the city was 97.4% White, 0.3% African American, 0.5% Native American, 0.3% Asian, 0.5% from other races, and 1.0% from two or more races. Hispanic or Latino of any race were 1.4% of the population.
There were 1,038 households of which 34.7% had children under the age of 18 living with them, 60.0% were married couples living together, 9.7% had a female householder with no husband present, 5.6% had a male householder with no wife present, and 24.7% were non-families. 19.6% of all households were made up of individuals and 4.9% had someone living alone who was 65 years of age or older. The average household size was 2.68 and the average family size was 3.04.
The median age in the city was 38.9 years. 24.8% of residents were under the age of 18; 7.3% were between the ages of 18 and 24; 26.4% were from 25 to 44; 32.9% were from 45 to 64; and 8.6% were 65 years of age or older. The gender makeup of the city was 49.6% male and 50.4% female.
As of the census of 2000, there were 2,376 people, 850 households, and 669 families residing in the city. The population density was 479.2 people per square mile (185.0/km²). There were 935 housing units at an average density of 188.6 per square mile (72.8/km²). The racial makeup of the city was 97.56% White, 0.17% African American, 0.63% Native American, 0.08% Asian, 0.51% from other races, and 1.05% from two or more races. Hispanic or Latino of any race were 1.68% of the population.
There were 850 households out of which 42.7% had children under the age of 18 living with them, 60.5% were married couples living together, 12.9% had a female householder with no husband present, and 21.2% were non-families. 15.1% of all households were made up of individuals and 3.4% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.08.
In the city, the population was spread out with 29.4% under the age of 18, 9.9% from 18 to 24, 31.8% from 25 to 44, 22.8% from 45 to 64, and 6.1% who were 65 years of age or older. The median age was 32 years. For every 100 females, there were 97.3 males. For every 100 females age 18 and over, there were 97.4 males.
The median income for a household in the city was $51,211, and the median income for a family was $56,029. Males had a median income of $36,389 versus $25,285 for females. The per capita income for the city was $20,278. About 6.3% of families and 7.4% of the population were below the poverty line, including 10.9% of those under age 18 and none of those age 65 or over.
Byrnes Mill Missouri neighborhoods include: Lake Montowese, Mill Road, Olde Mill Estates, Rual road, Vogt, Walnut Ridge