Duncan is a city located in Oklahoma. With a 2020 population of 21,778, it is the 21st largest city in Oklahoma and the 1729th largest city in the United States. Duncan is currently declining at a rate of -1.45% annually and its population has decreased by -7.05% since the most recent census, which recorded a population of 23,431 in 2010. Duncan reached it's highest population of 23,443 in 2010. Spanning over 48 miles, Duncan has a population density of 508 people per square mile.
The average household income in Duncan is $59,592 with a poverty rate of 16.61%. The median rental costs in recent years comes to $689 per month, and the median house value is $102,600. The median age in Duncan is 37.9 years, 35.9 years for males, and 39.5 years for females. For every 100 females there are 90.7 males.