Duncan is a town in Greenlee County, Arizona, United States. As of the 2010 census, the population of the town was 696. In 2015 the estimated population was 799.
Duncan is located in southern Greenlee County at 32°43′33″N 109°5′52″W / 32.72583°N 109.09778°W / 32.72583; -109.09778 (32.725828, -109.097686). U.S. Route 70 passes through downtown, leading west 39 miles (63 km) to Safford, Arizona, and southeast 35 miles (56 km) to Lordsburg, New Mexico, and Interstate 10. Arizona State Route 75 leads north from Duncan 28 miles (45 km) to Clifton.
According to the United States Census Bureau, the town of Duncan has a total area of 2.2 square miles (5.6 km), all of it land.
As of the census of 2000, there were 812 people, 294 households, and 206 families residing in the town. The population density was 317.6 people per square mile (122.5/km²). There were 384 housing units at an average density of 150.2 per square mile (57.9/km²). The racial makeup of the town was 81.77% White, 0.49% Black or African American, 0.86% Native American, 0.12% Asian, 13.55% from other races, and 3.20% from two or more races. 31.53% of the population were Hispanic or Latino of any race.
There were 294 households out of which 42.2% had children under the age of 18 living with them, 46.3% were married couples living together, 17.7% had a female householder with no husband present, and 29.6% were non-families. 25.9% of all households were made up of individuals and 12.9% had someone living alone who was 65 years of age or older. The average household size was 2.76 and the average family size was 3.33.
In the town, the population was spread out with 35.2% under the age of 18, 10.6% from 18 to 24, 22.2% from 25 to 44, 21.2% from 45 to 64, and 10.8% who were 65 years of age or older. The median age was 28 years. For every 100 females, there were 90.6 males. For every 100 females age 18 and over, there were 91.3 males.
The median income for a household in the town was $27,368, and the median income for a family was $33,750. Males had a median income of $32,232 versus $18,333 for females. The per capita income for the town was $13,642. About 14.0% of families and 16.5% of the population were below the poverty line, including 17.4% of those under age 18 and 23.2% of those age 65 or over.