[1] This 35-mile (55 km) route from the small community of Kapapala (near present-day Pahala) had been used in Ancient Hawaii to make offerings to Pele during eruptions.

The name comes from ʻāina pō in the Hawaiian language which means "darkened land", due to heavy clouds at the mid-elevation sections.

In areas where the trail was hard to discern, rock cairns marked the way, placed to be visible along the skyline as travelers moved upwards.

[2] In 1794, Archibald Menzies, a naturalist on the Vancouver Expedition, used the trail and about 100 Hawaiian porters to reach the summit and measure its elevation with a barometer.

[4] Lieutenant Charles Wilkes of the 1840 United States Exploring Expedition first attempted to use a shorter route, but resorted to the Ainapo trail after making much slower progress than he planned in his trip to the summit.