SR 36 begins in Unicoi County as the unsigned companion route of US 19W at the Tennessee-North Carolina state line.

US 19W/SR 36 goes west as a narrow 2-lane highway through rural mountainous areas before curving to the north and having a y-intersection with SR 352 (Old US 23).

SR 36 then continues northeast, paralleling the South Fork Holston River to Colonial Heights, where it has an interchange with Interstate 81 (exit 59).

[4] In 1952, US 23 was rerouted southwest of Ernestville, along SR 81 through Flag Pond and Sam's Gap into North Carolina; its old alignment remained part of US 19W/SR 36.

In 1970, The first segment of a four-lane freeway, designated SR 137, was opened between Johnson City and Kingsport.