SR 139 was established around 1950 running between US 25W northwest of Kodak and SR 66 near Douglas Dam. After I-40 was completed in 1975, SR 66 was relocated onto a new route between Sevierville and I-40 and a concurrency with I-40 route, and SR 139 was truncated to the new route of SR 66. On July 1, 1983, as part of a statewide takeover of local roads, SR 139 was re-extended onto its original route between the parkway and Douglas Dam, and extended along the old route of SR 66 to Dandridge. At this time, the old stretch of SR 66 between Sevierville and Douglas Dam became SR 338.