The road begins as a continuation of California State Route 182 12 miles (19 km) north of Bridgeport.

SR 338 follows the river northeast for about 3 miles (4.8 km) before diverting northwest, away from the water's course.

The route crosses several small creeks as it heads north entering the Smith Valley.

[2][4] An unimproved road connecting the Smith Valley to Sweetwater and Bridgeport existed as early as 1917.

[1][6] Earthwork improvements were made on SR 22 by 1936,[7] but the northern end of the route would not be paved until 1948 with the remainder receiving pavement two years later.