For explorers the existence, length and location of the Siachen glacier was a matter of discussions. In 1821, W. Moorcroft passed near its snout and first acknowledged its existence. In 1835 G.T. Vigne approached it from the west trying to reach the Bilafond la, but he never guessed the existence of such a large glacier across the divide. In 1848 Henry Starchy was the first to discover the existence of the Saichar glacier and ascended it for two miles from the snout in the Nubra valley. In the same year, Dr. Thomas Thompson also reached the glacier followed by F. Drew in 1849-50. E.C. Ryall of the Survey of India sketched the lower part in 1861. But he ascribed to it a length of only sixteen miles.
During his famous second Karakoram journey in 1889, Sir Francis Younghusband (then Colonel) approached the area over the Urdok valley. He was exploring the area to locate a crossing into the Indian Sub-continent. Following a side valley of the Urdok glacier, he reached Turkestan la (North). Looking down to the Siachen glacier from the north he felt that this was the main axis of the Karakoram. His explorers instincts were correct but, in absence of maps, he was not sure where he was standing. His belief was finally confirmed by Dr. T.G. Longstaff in 1909. In fact, it was Dr. Longstaff with Dr. Arthur Nv and Lt Slingsby who were the first real explorers to traverse this great glacier. At first, they crossed over the Bilafond la (or, Saltoro pass, as Dr. Longstaff would have preferred to call it) and named the glacier in the east as Teram Shehr (destroyed city) and peaks as Teram Kangri group. After retreating by the same route, he went down the valley and approached the Siachen via the Nubra valley. Dr. Longstaff climbed up from the Siachen snout in the south and observed the same peaks, as he had identified them from Bilafond la. Thus, he conclusively proved the length of Siachen glacier and the actual location of the Turkestan la (North). This was an important discovery as it now established the true boundaries of the Karakoram. What he wrote is quoted often:
Younghusband was a true prophet. Col Burrand of the Survey had suspected the truth. The avalanche-swept pass, whose foot Younghusband had reached 20 years before, was on the main axis of the Karakoram range which thus lay miles farther north than had been believed. We had stolen some 500 sq miles from the Yarkand river systems of Chinese Turkestan, and joined it to the waters of the Indus and the Kingdom of Kashmir.