The National Tropical Botanical Garden (originally the Pacific Tropical Botanical Garden) was created by Congressional Charter as a not-for-profit institution, dedicated to tropical plant research, conservation, and education.

Following the enactment of this charter in 1964, the founding Trustees and other supporters of the new organization began looking for a location for its first garden. Although a number of sites in the Hawaiian Islands were discussed, the “short list” included a location on the island of O‘ahu and land in the Lāwa‘i Valley on the island of Kaua‘i. The initial purchase was 171 acres at Lāwa‘i in 1970. The site consisted of a section of the floor of the valley, largely planted in sugar cane, and the steep sloping sides of the valley. This became known as the Lāwa‘i Garden.

The development of a garden site outside the town of Hāna on the Hawaiian island of Maui began in 1972. The gift and purchase of the two parcels which comprised this site was completed in 1974. Kahanu Garden was named in honor of the donor family, whose roots there dated back to the days of Hawaiian chiefs. A large native pandanus forest fringed the property. The site contained a major archaeological and cultural feature, Pi`ilanihale, which had previously been designated a National Historic Landmark. The annual rainfall in the area, as well as deep rich soils, made the new garden an ideal place to plant species from the humid tropics.