In the article the experience of using historical materials in landscape mapping of the earlier developed territories of the south of Eastern Siberia is presented. More than a hundred years ago, the Resettlement Department of the Main Department of land management and agriculture has conducted soil and botanical researches in the upper reaches of the Lena river for develop the tillage. The results of these researches were the basis for the reconstruction of the landscape structure of the territory of the key area of the Lena-Angara interfluves in the late XIX – early XX century. The resulting map and analysis of retrospective materials made it possible to reveal a high proportion of the transformed states of geosystems. The reason for this was frequent forest fires. The comparative analysis of the reconstructed map with the current state of the landscape structure showed the increase of the area of post-fire coniferous-small-leaved forests. This indicates a tendency of constant reduction of natural mountain-taiga cedar and larch forests.