It probably started as a foot path, then progressively improved. The 39-mile roadway was first constructed between 1916 and 1922. Using prison labor, they built the road setting rocks, rolling with a steam roller, and pouring tar heated in a pot. A camp for the prisoners who built the road was located on the down slope side of the Saddle Road intersection, where a grove of eucalyptus trees stands today.
Then, the Waimea-Kona road was rebuilt and straightened. “The formal opening of the new belt road on the island of Hawaii, July 22, 1933, was an important occasion, attended by the Governor and his party from Honolulu and many excursionists.” “The proposal has been made that the new road be named ‘Mamalahoe,’ commemorating the famous edict by King Kamehameha I, “the Law of the Splintered Paddle” making Hawaii’s highways safe for the traveler.”