Former Hawaii Route 21 on Wainaku Street in Hilo

Hawaii Route 21 was the one of the original Big Island State Routes designated in 1955. The highway followed mostly Wainaku Street from Hawaii Route 19 near Wainaku south to Hawaii Route 20 in downtown Hilo. Wainaku Street prior to 1950 was part of the larger Mamalahoa Highway (Hawaii Belt Road). The early importance of Wainaku Street can be seen in the form of the 1919 era Wailuku River Bridge (pictured as the blog cover) which was one of the first arch concrete spans in Hawaii. Hawaii Route 21 was ultimately deleted in the 1960s after it was removed as a Federal Aid corridor.

Part 1; the history of Hawaii Route 21 and Wainaku Street

Wainaku Street was the original main road north out of downtown Hilo over the Wailuku River. The street was also part of the wider Mamalahoa Highway (Hawaii Belt Road) which circled the entire Big Island. Nearby Bridge Street (now Puueo Street) provided a secondary road crossing of the Wailuku River.

Mamalahoa Highway was declared by royal decree in 1783 via the Law of the Splintered Paddle. The law was conceived based off an incident Kamehameha I was part of along the Puna coast. During said incident Kamehameha I and his men were conducting a shoreline raid when they encountered two Puna fisherman. While pursuing the fisherman across a lava field one of Kamehameha's feet was caught in a rock. The fishermen seized upon the opportunity to retaliate and struck Kamehameha in the head with a wooden paddle.

Kamehameha I opted to not retaliate against the fisherman and used the incident as the basis of the Law of the Splintered Paddle. The law essentially guaranteed safe passage to all travelers across the Hawaiian Islands and was used as a basis of Mamalahoa Highway on the Big Island. The highway corridor was rapidly developed across the Big Island and mostly annexed as early automotive roads. In 1919 one of the first arch concrete bridges in Hawaii was constructed along Wainaku Street at the Wailuku River to permit easier automotive access north of Hilo and the Mamalahoa Highway.

During 1950 the piers from the Hawaii Consolidated Railway Bridge at the Wailuku River were reused to construct a new highway bridge near the mouth at Hilo Bay. This then new bridge shifted Mamalahoa Highway east of Wainaku Street.

Wainaku Street was assigned as Hawaii Route 21 in 1955 when the Hawaii Route system was expanded to the Big Island. The Hawaii Route 21 corridor was 1.9 miles originating at Hawaii Route 19 near Wainaku. The highway followed Wainaku Street south over the Wailuku River and jogged to Hawaii Route 20 via Wailuku Drive and Kinoole Street.

According to Oscar Voss's hawaiihighays.com the corridor of Hawaii Route 21 was not long lived. The corridor appeared on maps of the Big Island until 1976, but internal Hawaii Department of Transportation documents suggest it was deleted during the late 1960s. The impedes for the deletion of Hawaii Route 21 seems to be the corridor of Wainaku Street being removed from Federal-Aid programs.

Part 2; a drive along former Hawaii Route 21 on Wainaku Street

Former Hawaii Route 21 and Wainaku Street can be accessed in both directions from modern Hawaii Route 19 north of downtown Hilo. Wainaku is still used as a control destination on guide signs.

Along southbound Wainaku Street an abandoned road overpass can be found approaching Halaulani Place. United States Geological Survey maps indicate the long-overgrown overpass to be part of an older alignment of Halaulani Place.

Southbound Wainaku Street crosses the 1919 era Wailuku River Bridge and ends at Wailuku Drive in downtown Hilo. Hawaii Route 21 would have followed Wailuku Drive and Kinoole Street to a terminus at Hawaii Route 20/Waianuenue Avenue (now Hawaii County Route 200).