The navigable
Noord River made the mountain more accessible than the other snow-covered peaks of
Dutch New Guinea and the Dutch organized a series of scientific expeditions in the early 20th century to reach the equatorial eternal snow and climb the mountain. The leader of the first two expeditions was the diplomat and amateur biologist
H.A. Lorentz. Each expedition was accompanied by soldiers, porters, and
Dayaks, who were employed for their expertise with boat journeys. In July 1907, the first expedition established
Camp Alkmaar near where the Noord River, since 1910 known as the
Lorentz River, became unnavigable (), but was unsuccessful in penetrating the highest mountain range. The
Second South New Guinea Expedition also used Camp Alkmaar, from where it left on October 9, 1909. A group of nine, including Lorentz and Jan Willem van Nouhuys, were the first to reach the eternal snow of New Guinea at a height of on November 8, 1909. From the ridge, they observed a large lake to the north, which Lorentz named
Lake Habbema (), after a member of the expedition. No attempt was made to reach the Wilhelmina summit. The return trip was severe; with the loss of four expedition members, the explorers finally returned to Camp Alkmaar in mid-December. The summit was first reached in 1913 during the
Third South New Guinea Expedition, which lasted from September 1912 to April 1913 and followed the same route. It was led by Alphons Franssen Herderschee, an officer of the
Royal Netherlands East Indies Army, and it aimed to research the soils, flora, and fauna of the region that lay above 2,300 metres. Other expedition members were the zoologist
Gerard Martinus Versteeg, the botanist
August Adriaan Pulle, the geologist
Paul François Hubrecht, and
J.B. Sitanala, an Indonesian
GP. Herderschee also took over the role of
ethnographer. Including soldiers, porters, and Dayaks, the
baggage train had 241 members. They were divided up into several groups to carry out the different tasks in a time-effective way. Herderschee, Hubrecht, and Versteeg formed the summit team, which reached the
Wilhelminatop on 21 February 1913. The 1920-1922
Central New Guinea Expedition had as its goal to reach the mountain from the north coast over a route partially explored in a 1914 military expedition. On February 7, 1920, the first exploration, under the leadership of A.J.A. van Overeem started at the mouth of the
Mamberamo and followed the
Idenburg River. In October, they had climbed across the Doorman Mtns and reached the upper
Swart Valley (now Toli Valley). Here they made first contact with the
Lani people (a.k.a. the Western
Dani people), an agricultural people with whom they stayed for six weeks. Running out of time and food provisions, this expedition returned without climbing Wilhelmina. A follow-up expedition starting in June 1921 and led by J.H.G. Kremer, who was a surveyor the previous year, retraced the route, and via the upper
Baliem Valley and Lake Habbema reached the summit on 4 December 1921. Among the ascendants was Paul Hubrecht, who had been on the top in 1913 and noticed that the ice cap had retreated considerably since 8 years before. ==Notes==