The article presents a comprehensive study of the territorial structure of the state. The purpose of the article is to analyze the content of the concept of state structure, the elements of this concept are considered: the territory of the state, part of the territory of the state, administrative boundaries, the need and history of their establishment. The article points to the ethnos as a factor in the emergence of parts of the territory of the state and the establishment of a certain structure of the territory in this regard. The state structure is considered by the presence of parts or their absence. Parts of the territory in the process of developing state territorial construction can have a different status: from a territory (part) with limited sovereignty to autonomy within a centralized state. Territories (units) can conclude a union of territories with a single center and form two types of the most common types of territorial structure of the state - federation and confederation. The article analyzes the genesis of the federation, possible ways of development and its real results. The article provides a classification of federations by the method of formation and the concepts of creating a union of territories (parts), a comparison of the administrative-territorial structures of states and the principles of federalism on which they are created. In accordance with the logic of presentation, the article provides examples from the practice of state territorial construction.