Martinsburg is a town in Lewis County, New York, United States. The population was 1,433 at the 2010 census. The town is named after founding father, General Walter Martin.
According to the United States Census Bureau, the town has a total area of 76.1 square miles (197.1 km²), of which 75.8 square miles (196.3 km²) is land and 0.3 square miles (0.8 km²) (0.39%) is water.
The east town line is the Black River. The western part of Martinsburg is on the Tug Hill Plateau.
New York State Route 12 and New York State Route 26 are north-south highways through the town with NY-12 being the more easterly route.
At the 2000 census, there were 1,249 people, 473 households and 347 families residing in the town. The population density was 16.5 per square mile (6.4/km²). There were 627 housing units at an average density of 8.3 per square mile (3.2/km²). The racial makeup of the town was 98.00% White, 0.48% African American, 0.48% Native American, 0.24% from other races, and 0.80% from two or more races. Hispanic or Latino of any race were 0.48% of the population.
There were 473 households of which 34.9% had children under the age of 18 living with them, 61.3% were married couples living together, 7.2% had a female householder with no husband present, and 26.6% were non-families. 22.8% of all households were made up of individuals and 8.2% had someone living alone who was 65 years of age or older. The average household size was 2.64 and the average family size was 3.11.
28.3% of the population were under the age of 18, 7.8% from 18 to 24, 28.9% from 25 to 44, 22.3% from 45 to 64, and 12.7% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 103.4 males. For every 100 females age 18 and over, there were 103.2 males.
The median household income was $31,902 and the median family income was $35,978. Males had a median income of $26,705 compared with $20,682 for females. The per capita income for the town was $13,894. About 7.9% of families and 11.9% of the population were below the poverty line, including 18.3% of those under age 18 and 9.6% of those age 65 or over.