Marathon is a town in Cortland County, New York, United States. The population was 1,967 at the 2010 census.
According to the United States Census Bureau, the town has a total area of 25.1 square miles (64.9 km), of which 25.0 square miles (64.7 km) is land and 0.12 square miles (0.3 km), or 0.53%, is water.
U.S. Route 11 and Interstate 81 are important north-south highways, and New York State Route 221, an east-west highway, intersects the former at Marathon village.
The Tioughnioga River, part of the Susquehanna River watershed, crosses the town along the same course as Interstate 81 and US-11.
The south town line is the border of Broome County.
As of the census of 2000, there were 2,189 people, 814 households, and 598 families residing in the town. The population density was 87.7 people per square mile (33.8/km²). There were 861 housing units at an average density of 34.5 per square mile (13.3/km²). The racial makeup of the town was 98.49% White, 0.73% Black or African American, 0.14% Native American, 0.09% from other races, and 0.55% from two or more races. Hispanic or Latino of any race were 0.55% of the population.
There were 814 households out of which 39.9% had children under the age of 18 living with them, 57.4% were married couples living together, 10.7% had a female householder with no husband present, and 26.5% were non-families. 21.4% of all households were made up of individuals and 9.7% had someone living alone who was 65 years of age or older. The average household size was 2.69 and the average family size was 3.10.
In the town, the population was spread out with 30.7% under the age of 18, 6.0% from 18 to 24, 29.3% from 25 to 44, 21.5% from 45 to 64, and 12.5% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 94.9 males. For every 100 females age 18 and over, there were 90.8 males.
The median income for a household in the town was $34,274, and the median income for a family was $40,379. Males had a median income of $29,781 versus $22,125 for females. The per capita income for the town was $15,322. About 8.6% of families and 10.9% of the population were below the poverty line, including 12.3% of those under age 18 and 12.0% of those age 65 or over.