Mission Township is located in LaSalle County, Illinois. As of the 2020 census, its population was 4,019 and it contained 1,068 housing units.
Mission Township was given its name due to the church-riding ministers riding across to different churches in the township. One of these ministers, Jessie Walker, actually has a memorial at the United Methodist Church in Sheridan, which is the seat of the township.
The township is shares its western boundary with Serena Township, and its northern boundary with Northville Township. The township border is defined by where the Fox River goes southwest, turns south, then continues to go east, south, west, northwest, north, and then it then curves to go southwest again, forming an awkward "S" shape on the map.
The community of Sheridan resides at the beginning of the bends in the river, and the community of Norway resides where the river flows north, and then curves around to flow southwest. Millington resides along the river, northeast of Sheridan. The community of Newark resides along the county line within Kendall County, but the community is no more than 4 to 5 miles away from the river.
According to the 2021 census gazetteer files, Mission Township has a total area of , of which (or 98.68%) is land and (or 1.32%) is water.
As of the 2020 census there were 4,019 people, 1,102 households, and 791 families residing in the township. The population density was . There were 1,068 housing units at an average density of . The racial makeup of the township was 66.38% White, 24.73% African American, 0.35% Native American, 0.22% Asian, 0.00% Pacific Islander, 4.95% from other races, and 3.36% from two or more races. Hispanic or Latino of any race were 7.09% of the population.
There were 1,102 households, out of which 25.70% had children under the age of 18 living with them, 49.18% were married couples living together, 11.25% had a female householder with no spouse present, and 28.22% were non-families. 26.20% of all households were made up of individuals, and 6.40% had someone living alone who was 65 years of age or older. The average household size was 2.25 and the average family size was 2.59.
The township's age distribution consisted of 10.8% under the age of 18, 12.7% from 18 to 24, 42.2% from 25 to 44, 26% from 45 to 64, and 8.5% who were 65 years of age or older. The median age was 36.0 years. For every 100 females, there were 279.9 males. For every 100 females age 18 and over, there were 338.2 males.
The median income for a household in the township was $70,107, and the median income for a family was $77,083. Males had a median income of $55,179 versus $25,714 for females. The per capita income for the township was $20,656. About 3.4% of families and 6.8% of the population were below the poverty line, including 8.6% of those under age 18 and 3.4% of those age 65 or over.