A picturesque lane embowered by monkeypod and royal poinciana trees, Kaumakani Avenue is lined with plantation houses and buildings in various styles sitting on large lots and set back from the street by a boundaryless lawn. Terminating at the mill, this roadway was the focal point of the Hawaiian Sugar Company, accommodating a social hall, plantation office, and an array of skilled workers' cottages. The single-story, late-nineteenth-century social hall still retains such Victorian architectural elements as the shingled front-facing gable and a bracketed eave line. It now serves as a visitor center and base for plantation tours.
The reinforced-concrete plantation office designed by Guy Rankin, the Hawaiian Sugar Company's civil engineer, was one of the earliest buildings in Hawaii to be rendered in Spanish Mission Revival, and upon its opening in 1917, the Honolulu Advertiser found it to be “a surprise in the way of up-to-date construction that puts it over anything in the plantation office line that we have seen.” The concrete light posts gracing the avenue date from 1920 and were the earliest electric streetlights on Kauai. The Hawaiian Sugar Company was established in 1889 and remained in operation until July 1941, when it was acquired by C. Brewer. At that time, the plantation's name was changed to Olokele Sugar Company and the village became known as Kaumakani. The C. Brewer company undertook a major rebuilding program during 1946–1947 and the four single-wall, tongue-and-groove residences near the highway date from that revitalization episode. Several houses below the tennis court derive from more recent efforts, and a few of the late-nineteenth-century houses still stand along the road, including the board-and-batten nurses' cottage (c. 1900) at the corner of Kaumakani Avenue and Kaumualii Highway.
In 1994, Gay and Robinson, who owned the underlying land lease for the plantation, purchased the mill and assets from Olokele Sugar and has operated it since.