follows SR 20 from the intersection with US 72 at Muscle Shoals to I-65 east of Decatur, the entire stretch being four-laned.

It continues south to parallel the Tennessee River, heading east for just a mile as Coffee Road before junctioning with US 72 and US 43 at a Parclo.

and SR 20 turn to the direct east/west and eventually enter Lawrence County.

The routes continue east to the Morgan County line and enter Trinity.

This junction is limited because there is no direct connection between US 31 north and SR 20 west.

The routes continue north across the Tennessee River again and enter Limestone County.

SR 20 was also realigned to a much more direct route between Decatur and Huntsville, bypassing the town of Madison.

Beginning in the early 1980s, the eastern terminus of SR 20 began retreating to the west.

Origional sections of SR 20 can be found in the town of Mooresville, with an unusually wide two way road that is clearly visible from aerial views.

The old section becomes a divided highway before eventually merging into an access road that parallels I565 up to Greenbrier.