The area was first settled around 1817. The town of Mansfield was formed in 1830 from part of the town of Town of Little Valley. The town was first called "Cecilius". The name "Mansfield" was adopted in 1831. Mansfield had a post office by 1840. It is implied to still have a post office as late as 1933 but merged with the Little Valley post office some time before the establishment of ZIP Codes in 1963. The ZIP Code Tabulation Area for 14755, the ZIP Code for Little Valley, shows a clear 8 shape illustrating the territory each office covered.
As of the census of 2000, there were 800 people, 305 households, and 234 families residing in the town. The population density was 20.2 people per square mile. There were 540 housing units at an average density of 13.6 per square mile. The racial makeup of the town was 98.88% White, 0.12% African American, 0.75% Native American, 0.12% Asian, and 0.12% from two or more races. Hispanic or Latino of any race were 0.25% of the population. There were 305 households out of which 33.8% had children under the age of 18 living with them, 64.3% were married couples living together, 6.6% had a female householder with no husband present, and 23.0% were non-families. 19.3% of all households were made up of individuals and 6.9% had someone living alone who was 65 years of age or older. The average household size was 2.61 and the average family size was 3.00. In the town, the population was spread out with 27.9% under the age of 18, 6.3% from 18 to 24, 27.8% from 25 to 44, 27.4% from 45 to 64, and 10.8% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 108.3 males. For every 100 females age 18 and over, there were 103.9 males. The median income for a household in the town was $36,420, and the median income for a family was $37,500. Males had a median income of $27,614 versus $24,750 for females. The per capita income for the town was $21,700. About 6.3% of families and 8.0% of the population were below the poverty line, including 7.8% of those under age 18 and 2.4% of those age 65 or over. Much of Mansfield north of Five Points is agricultural land, with several farms in the area.
Dobbins Memorial State Forest - a state forest in the southern part of the town.
Eddyville - a hamlet in the north part of the town on County Road 14. The Mansfield town hall is in Eddyville, as is the town's only currently operating church, the nondenominational Solomon's Porch Ministries. Eddyville was also the site of the town's post office during its existence before it was closed some time in the early 20th century.
Eddyville Corners - The spot where County Roads 13 and 14 converge, north of Eddyville and west of Maples. A now-abandoned Baptist church is at this spot, as is a state-operated fish stocking outlet on Mansfield Creek.
Five Points - A location southwest of Eddyville near the town center on County Road 14. Five Points is the location of a county-operated landfill.
Maples - A hamlet east of Eddyville on County Road 13. The Mansfield fire department and highway barns are in Maples.
Orlando - A mostly unpopulated hamlet near the east town line on County Road 13.
