SH 15 was one of the original twenty five state highways proposed on June 21, 1917, overlaid on top of the Dallas-Louisiana Highway. From 1917 the routing mostly followed present day U.S. Highway 80 from Dallas to Wills Point. It continued on, routed along present day SH 64 from Wills Point into Tyler and up U.S. Highway 271 into Gladewater, and east along US 80 into Longview. On June 17, 1918, the section of SH 15 from Gladewater to Longview was transferred to SH 11. On January 21, 1919, an alternate route of SH 15 was designated east of Wills Point, going through Mineola to Gladewater, via US 80.