Duncan is a city and county seat of Stephens County, Oklahoma, United States. Its population was 22,310 at the 2020 census. Duncan is the birthplace of the Halliburton Corporation. Erle P. Halliburton established the New Method Oil Well Cementing Company in 1919. Halliburton maintains seven different complexes in Duncan plus an employee recreational park, but the corporate offices relocated first to Dallas and later to Houston.
Centrally located in Stephens County, Duncan became the county seat after Oklahoma achieved statehood in 1907. Oil wells opened in Stephens County in 1918 and led to rapid development. Cotton was a dominant crop until the Dust Bowl brought its decline, but cattle remain an important part of the economy. The Chisholm Trail passed to the east of Duncan prior to the town's founding, which is home to the Chisholm Trail Heritage Center.
The Chisholm Trail passed to the east of Duncan prior to the town's founding. An estima