This Sabah Society Monograph is devoted to commemorating 40 years since the Royal Society Expeditions to Mount Kinabalu, which was declared a national park in 1964. The Royal Society Expeditions (RSE) of 1961 and 1964 took place when Sabah was in transition from a British administered colony to an independent state within the Malaysian Federation. The first RSE was the last of a long series of major scientific expeditions undertaken during the colonial era. The First RSE was also the first team to undertake an exploration of the long and difficult Eastern Ridge of Kinabalu. All previous explorations of the mountain had focused on its western side.