The article studies a historical source that previously was not in the focus of research - travel notes of the outstanding Russian merchant of the 19th century, gold miner, and discoverer of the Northern Sea Route Mikhail Konstantinovich Sidorov, which he wrote during a trip to the North Caucasus and Transcaucasia in August – September 1878. It aims to analyze the notes, characterize their content, and reveal the information potential for further study of the processes that took place among the forming Russian bourgeoisie in the post-reform period and testifying to the interest of Russian capital in the study and economic development of the outskirts of the empire. The research relies on the intellectual history approach, which involves the study of the mentality, the emergence and subsequent transformation of various ideas and cultural orientations inherent in a particular social stratum, in this case, the Russian merchant class. The travelogue provides valuable information characterizing the methods of work of its author, who already had extensive experience in the exploration and development of ore and oil fields in Siberia and the lower reaches of the Pechora, in collecting and recording primary information about minerals located in the region, local mining and manufacturing enterprises, his range of interests and, to some extent, ideological attitudes (in particular, adherence to the ideals of the Russian Orthodox Church). The surviving notes are, first of all, a brief fixation of what was seen, necessary for subsequent comprehension and generalization in the form of articles and reports, as well as formulations of practical recommendations on the prospects for further economic development of the territories that recently became part of the Russian Empire. In addition to information about the economic capacities of the region, M. K. Sidorov’s notes reflect the author’s impressions of visiting several local towns and villages, exploring natural and historical attractions, communicating with residents of different ethnicities. As a whole, the source under consideration expands the anthology of diaries and memoirs known to date that have arisen among the Russian peasantry, contains information about the economic and socio-cultural state of the Caucasus in the second half of the 19th century, emphasizes the interest and active participation of Russian business circles in the study and economic development of the region.