It then descends along Warthan Canyon to the town of Coalinga in the agricultural Central Valley, where it briefly runs concurrently with SR 33.

[2] SR 198 then intersects Interstate 5 (I-5) in Fresno County near the Harris Ranch Airport before becoming a freeway west of Lemoore.

The first bond issue, approved by the state's voters in 1910, included the road from Visalia west to Hanford, connecting the two county seats with the central north–south highway (Route 4, now SR 99).

The third bond issue, passed in 1919, included a further extension east from Visalia to Sequoia National Park.

[11] The portion east of Interstate 5 near Coalinga was added to the California Freeway and Expressway System in 1959,[12] and parts of it have been built as such.

Developers are interested in building distribution warehouses in Kings County because of its strategic location midway between the Los Angeles and San Francisco Bay areas, but they are currently turned off by the lack of freeway access.

[19] Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage.