SR 306 begins at the road to Barrack Cortez Mine, just east of Gold Acres in central Lander County.

The highway passes briefly through Whirlwind Valley before reaching Interstate 80, where SR 306 terminates at the Beowawe Interchange (exit 261).

[4] By 1933, the southern end of SR 21 had been extended beyond Austin, branching from US 50 just west of town and heading in a southwesterly direction towards Ione.

In this process, the paved portion of the highway between Crescent Valley and US 40/I-80 north of Beowawe was redesignated as State Route 306.

[8] The rest of SR 21 remained on official Nevada maps for a short time, but was ultimately removed from the state highway system by 1982.