The article considers the beginning of the Russian conquest of Transbaikal area. The report of the voivodes Peter Golovin and Matvey Glebov to the Russian Tsar Mikhail Fyodorovich Romanov verifies that the first Russian winter hut on the river Vitim was built in 1639 by the Cossack Ataman Maksim Perfilyev. The winter hut was in the Kotomary (Kutomaly) river mouth. The exploration of the Vitim was continued by Enaley Bakhteyarov. The explorers obtained information on the river Shilka, Daur people and silver deposits from the Tungus.