State Route 58 between Santa Margarita and Buttonwillow is a winding mountain road through a thinly populated area. From its westernmost terminus at US 101 near Santa Margarita, a few miles north of San Luis Obispo, SR 58 heads east along the former US 101 (El Camino Real) for one mile. SR 58 then heads east and up the winding mountain road, passing through a thinly populated area and an intersection with SR 229. Alternatives such as SR 46 to the north or SR 166 to the south are recommended, as much of this section of SR 58 is prohibited to truck traffic. However, this section of SR 58 does pass through the Carrizo Plain, which is known for its scenic beauty and geological features, including the San Andreas Fault. SR 58 then takes another winding road before joining with State Route 33 (SR 33) in the small town of McKittrick. SR 33 then splits at the north end of McKittrick before SR 58 then enters another, but brief winding road. SR 58 then proceeds northeast for several miles before changing to an east-west alignment and reaching Buttonwillow. A few miles later, SR 58 has an interchange with Interstate 5 (I-5). Approximately east of I-5, SR 58 briefly joins SR 43 before continuing east and eventually reaching the Bakersfield city limits.