The region was destroyed by the Sullivan Expedition on August 13, 1779, which fought at the Battle of Newtown, just west of the current town of Chemung. The first clear record of settlement dates to about 1786. The town of Chemung was established in 1788 as the original town in the region. Chemung lost territory when Tioga County was formed in 1791. The town of Newtown was taken from Chemung in 1792. Chemung was incorporated in 1788 into Montgomery County, at the time of that town's formation. Subsequently, the town of Chemung lost more territory to form all or parts of Erin, Baldwin, and Ashland. The Chemung District School No. 10, Dr. Hovey Everett House, and Riverside Cemetery are listed on the National Register of Historic Places.
As of the census of 2000, there were 2,665 people, 969 households, and 749 families residing in the town. The population density was 53.9 people per square mile. There were 1,054 housing units at an average density of 21.3 per square mile. The racial makeup of the town was 97.64% White, 0.53% African American, 0.26% Native American, 0.19% Asian, 0.45% from other races, and 0.94% from two or more races. Hispanic or Latino of any race were 0.83% of the population. There were 969 households, out of which 36.9% had children under the age of 18 living with them, 64.2% were married couplesliving together, 7.2% had a female householder with no husband present, and 22.7% were non-families. 17.2% of all households were made up of individuals, and 7.6% had someone living alone who was 65 years of age or older. The average household size was 2.71 and the average family size was 3.03. In the town, the population was spread out, with 28.0% under the age of 18, 6.8% from 18 to 24, 29.3% from 25 to 44, 23.5% from 45 to 64, and 12.4% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 101.9 males. For every 100 females age 18 and over, there were 99.7 males. The median income for a household in the town was $35,167, and the median income for a family was $37,885. Males had a median income of $29,844 versus $22,958 for females. The per capita income for the town was $15,201. About 8.5% of families and 11.7% of the population were below the poverty line, including 15.9% of those under age 18 and 1.1% of those age 65 or over.
Wells Spicer, judge who presided over preliminary hearing to see if Virgil, Wyatt, and Morgan Earp as well as Doc Holliday would stand trial for murder following the Gunfight at the O.K. Corral; also was defense attorney for John D. Lee in his trial for his involvement in the Mountain Meadows massacre.
