History of Science and Engineering Annotation << Back History of the Theory of Boundary Layer (XIX - XX Century) Plotkina V.A. Starodubtcev P.A. In this research paper shows a scientific analysis of the development of the theory of hydrodynamic and thermal boundary layers at the junction of two centuries. Based on theoretical and experimental studies, is a timeline of historical events of the theory of the boundary layer. The analytical background in the study of the boundary layer, formulated on the basis of theoretical and experimental studies of well-known scholars in the field of experimental fluid dynamics and aerodynamics. This article includes key terms and definitions that reveal the need to study the theory of the boundary layer. Considerable attention is paid to the premises of origin of the terms – the hydrodynamic and thermal boundary layer, as well as laminar and turbulent flow. Provides basic information about the most important historical discoveries at the turn of the nineteenth and twentieth centuries in the history of the application of the boundary layer. This publication shows the future development and feasibility study of the historical aspect of the theory of the boundary layer. Keywords: The hydrodynamic and thermal boundary layer; an ideal fluid; friction resistance; suction of the boundary layer; laminar and turbulent flow. Contacts: E-mail: vika_plotkina@mail.ru Pp. 03-12.