The Great Northern Expedition or Second Kamchatka expedition was one of the largest organised exploration enterprises in history, resulting in mapping of the most of the Arctic coast of Siberia and some parts of the North America coastline, greatly reducing the "white areas" on the maps. The endeavour was initially conceived by Russian Emperor Peter I the Great and implemented in practice by Russian Empresses Anna and Elizabeth. The main organiser and leader of the expedition was Vitus Bering, who earlier had been commissioned by Peter I to lead the first Kamchatka expedition. The Second Kamchatka expedition lasted roughly from 1733–1743 and later became called the Great Northern due to the immense scale of its achievements.