The Haleakalā Highway is a 37-mile road from Kahului to the summit of Haleakalā, with the last 10.6 miles within the park. Construction of the road from the park boundary to White Hill began in 1933 and was completed in 1935. Certain measures were made to minimize the negative impact to the environment as well as harmonize the road with its surroundings including covering rocks to match the shade of the stone masonry work. The road was improved and expanded during a nationwide initiative from 1956-1966 to modernize the Park Service which was called the Mission 66 Program. The Kalahaku and Leleiwi Overlooks and Red Hill Observatories were built during this time.
The current alignment of the Halemau'u Trail was built from 1935-1936 by the Civilian Conservation Corps because the old alignment was continuously being damaged by heavy rains. The trail was widened to a standard width and cemented rock walls and guardrails installed. The work required blasting sections with explosives and packing in materials using mules. The trail exhibits many of the characteristics of the naturalistic and rustic design styles of early NPS development which used native materials and integrated the natural landform and character of each site.
The Haleakalā Visitor Center, historically known as the Haleakalā Observation Station, is situated at the edge of the crater at 9,800 feet. Built in 1936, it was intended to be the major destination for visitors; providing sweeping views into the crater, as well as, a place to rest and get park information. This structure was part of early NPS development of the Haleakalā Section of Hawai'i National Park and is a good example of NPS rustic style architecture. Designed by NPS architect Merel Sager, the walls were formed with lava stone so it looked like it was merging with its surroundings and was part of the landscape.
Red Hill, or Pu'u 'Ula'ula, is a cinder cone southwest of White Hill and the true summit of Haleakalā at 10,023 feet. From 1941 to 1948 it was occupied by the Army who built various facilities on it. It was not until 1961 that the military facilities were removed and the Red Hill Observatory was constructed from 1962-1963. The buildings, stairs and parking lot were designed by NPS Architect Cecil Doty who was a prominent architect during the Mission 66-era of NPS development. Mission-66 architecture was more modernist in style versus early NPS architecture which was more rustic.
The nēnē, or Hawaiian goose, were extirpated (wiped out) from Maui by the 1890s. They were reintroduced to Haleakalā via the release of captive-raised birds. In 1962, nēnē from England and the Island of Hawai‘i were delivered to Maui and were carried into the crater by park rangers and naturalists and Maui Boy Scouts. They strapped on boxes holding geese and hiked 9.8 miles to Palikū where the geese were temporarily released in an open-top pen until they adapted to their surroundings. About 500 nēnē were released in Haleakalā National Park between 1962 and late 1970s. Today, there are about 250-350 nēnē in the park. The nēnē has been the official State Bird of Hawai‘i since 1957 and was put on the Federal endangered species list in 1967.
The Puʻu Nianiau area of Haleakalā National Park was used by the U.S. Army as a base camp from 1941 to 1946 for facilities being operated at the summit of Haleakalā. After the Armyʻs departure, base camp buildings were used in 1947 for the Haleakalā Mountain Lodge by Robert "Boy" von Tempsky who held a concession with the park. Mr. von Tempsky offered saddle and pack trips through the crater as well as bus transportation from docks, landing fields and hotels in Maui. The name of the facility was changed to the Silversword Inn under new managers in 1958 and closed in 1961. Today, the buildings are used by the NPS for offices, workshops and storage.