Beginning in 1876, the nearby Great Western Cattle Trail was used to drive cattle north from Texas to market. The community of Mangum began in 1882 when Henry Clay Sweet established it on land granted to A. S. Mangum by the state of Texas. The Mangum post office was established April 15, 1886. This part of Texas (old Greer County) was given to Oklahoma in 1896. During Mangum's early days, the community's economy largely depended on very large cattle ranches owned or leased by land companies such as the Day Land and Cattle Company of Texas and the Franklyn Land and Cattle Company, an English syndicate. During those very early days, the local cowboys called Mangum "Tin City" because so many tin cans were unrolled and nailed over the wooden planks that served as sidewalks.