Oahu's Kamehameha Highway (marked in orange above), and Farrington Highway (marked in blue above), are two long surface routes that loop around different parts of the island, continually changing route numbers along the way, and shifting from state to county jurisdiction and back again. Those highways, along with the Kalanianaole Highway around the southeast corner of Oahu (not highlighted above), were the island's main through routes before the Interstates were completed. The map above and the following discussion are provided to minimize confusion over the scattered appearances of the above highways throughout the Oahu route lists.

The Kamehameha Highway is generally assumed to be named for the first monarch reigning over all the Hawaiian islands, King Kamehameha I ("the Great"), rather than his four less illustrious successors in the Kamehameha dynasty (most of whom have lesser roads and highways named specifically for them). It begins near Kailua on Oahu's windward (east) coast, heading north as state route . A few miles to the north, as it passes through downtown Kaneohe, it follows former county route ( now bypasses Kaneohe). It continues as north of Kaneohe, all the way around the north shore of Oahu to Haleiwa. There the Kamehameha Highway changes to an unnumbered county road passing through downtown Haleiwa (bypassed by another new segment), then becomes at Weed Circle. From there, the Kamehameha Highway proceeds south through central Oahu on , until Wahiawa where it becomes as it passes through the town (while bypasses it to the west). The highway then resumes as south of Wahiawa. After a short break around the - interchange (which obliterated part of the old highway), it continues southeast past Pearl Harbor, to exit 15, after it is concurrent with Nimitz Highway for about three miles under the Airport Viaduct. At the other end of the viaduct, at exit 18, the Kamehameha Highway peels away from the Nimitz Highway as , but only for about 500 feet until it turns into part of former state route Dillingham Boulevard the rest of the way into downtown Honolulu.

The Farrington Highway, named for former territorial governor and newspaper publisher Wallace Rider Farrington, is a broken loop through western Oahu. It begins north of Pearl Harbor, as part of branching off from the Kamehameha Highway, then runs parallel to and south of , changing quickly to then before continuing west as another part of former state route , now an unnumbered county road. At the west end of it turns northwest along the leeward (west) coast as . Then the Farrington Highway turns into a rugged unpaved road, former (proposed?) state route and now permanently closed to through traffic, about three miles southeast of Kaena Point at the northwest corner of Oahu, and continuing to the point and then about three miles east along the north shore. From there the pavement resumes and the highway becomes , ending south of Haleiwa near the Kamehameha Highway.