 It was founded in 1635 as an "ostrog" by the Cossacks led by Pyotr Beketov, sited on the left bank of the Lena opposite the mouth of the Olyokma River.The outpost was later moved a few kilometers upstream, to a location less prone to flooding in spring.As the junction for river traffic on the Lena and Olyokma, it was the base for Russian expeditions further east and eventually became a trade center on the river route to Yakutsk.