Cotton was a dominant crop until the Dust Bowl brought its decline, but cattle remain an important part of the economy.

Halliburton maintains seven different complexes in Duncan plus an employee recreational park, but the corporate offices relocated first to Dallas and later to Houston.

[5] An estimated 9,800,000 Longhorn cattle were herded up the trail between Texas and Abilene, Kansas, during its existence.

After learning that an extension of the Chicago, Rock Island and Pacific Railroad was being built from Kansas to Texas, Scotsman William Duncan brought his wife, parents, and other relatives and created a trading post situated at the intersection of the north-south Chisholm Trail and the east–west military passage between Fort Arbuckle and Fort Sill.

Many of the city's first buildings were wood frame but were replaced by sandstone and brick structures after natural disasters destroyed them.

Oil wells opened in Stephens County in 1918 led to rapid development in Duncan.

[5] Shacks were prohibited immediately following the opening of the wells and other regulations were also put in place to channel the growth in an organized manner.

[6] Works Progress Administration projects meant to rebuild the economy after the Great Depression resulted in a public library, a senior high school, a stadium, a pool, a school and auditorium for the black community, an armory, and numerous bridges and sidewalks.

[6] Duncan expanded its city limits during an economic surge brought on by World War II.

[9] State lawmakers designated the city as Oklahoma's official "Crape Myrtle Capital".

[14] The downtown area lies between Walnut and Willow Avenues, from the railroad tracks to Highway 81.

Halliburton maintains seven different complexes in Duncan plus an employee recreational park, but the corporate offices relocated first to Dallas and later to Houston.

[6] The city has been home to a number of banks and doctors since its early settlement, and both continue to be well represented today.

[23] The Stephens County Historical Museum contains displays and artifacts from the land run and early settlement in the area.

[24] In 1974 the museum moved to the NRHP-listed old National Guard Armory in Fuqua Park, built in 1936-1937 as a WPA project.

[24] The city holds an annual county fair and top-rated livestock events year round.

[28] A socialist-leaning newspaper titled Justice was published by Wiley Edgar (Ed) Chives during 1907, the year of Oklahoma's statehood.

[33] Halliburton Field (KDUC; FAA ID: DUC), owned by the City of Duncan and located two miles south, has a paved 6326’ x 100’ runway.