SR 66 begins as a primary highway in Sevier County in Sevierville at an intersection with US 441/US 411/SR 35/SR 71 (Chapman Highway/Forks of the River Parkway/Main Street) in downtown.

The highway then becomes divided at the intersection with Allensville Road and continues north through a long major business district and has a concurrency with SR 338 (Douglas Dam Road/Boyds Creek Highway) before crossing a bridge over the French Broad River to leave Sevierville and enter Kodak.

After passing through some neighborhoods, SR 66 becomes signed as it splits off from US 25W/US 70/SR 9 to the northeast and leaves Dandridge as Valley Home Road.

US 11E/SR 34/SR 66 then continue northeast through farmland to pass through Whitesburg and have an extremely short concurrency with SR 113 before crossing into Hawkins County.

They then have an intersection with Old Highway 70 before crossing the Hugh B Day Bridge over Cherokee Lake/Holston River and entering Rogersville.

It then turns right and crosses a bridge over the Clinch River before coming to an end at an intersection with SR 33 just south of downtown.

This section stretched from Boyds Creek Highway (SR 338) to Nichols Street and began of July 15, 2009 and was completed on November 18, 2011.

The middle section from Douglas Dam Road to Boyds Creek Highway began in March 2012 and was completed in the summer of 2016, after multiple delays.